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Recent regional climate cooling on the Antarctic Peninsula and associated impacts on the cryosphere
... In spite of the apparent hiatus in warming in the first decade of the 21 st century (still explainable by natural climate variability; Turner et al. 2016;Oliva et al., 2017), with associated impacts on the cryosphere (Oliva et al. 2017, Engel et al. 2018Christie et al., 2022), Antarctic Peninsula temperature is projected to continue rising faster than the global average (IPCC, 2021). The increasing air temperatures presage the increasingly negative glacier mass balance (Slater et al., 2021), pronounced desiccation of the ice-free areas of James Ross Island (JRI) following the glacier retreat and enhanced active layer thawing (ATCM 2015). ...
... In spite of the apparent hiatus in warming in the first decade of the 21 st century (still explainable by natural climate variability; Turner et al. 2016;Oliva et al., 2017), with associated impacts on the cryosphere (Oliva et al. 2017, Engel et al. 2018Christie et al., 2022), Antarctic Peninsula temperature is projected to continue rising faster than the global average (IPCC, 2021). The increasing air temperatures presage the increasingly negative glacier mass balance (Slater et al., 2021), pronounced desiccation of the ice-free areas of James Ross Island (JRI) following the glacier retreat and enhanced active layer thawing (ATCM 2015). ...
... This was followed by cooling in the Late Holocene Neoglacial period (Čejka et al., 2020), starting ~2 ka (kiloanni = thousand years) BP (= before present, i.e. 1950 CE), when local glaciers advanced (e.g., Carrivick et al., 2012;Kaplan et al., 2020;Simms et al., 2021). Subsequent warming in recent centuries (Mulvaney et al., 2012;Simms et al., 2021) accelerated during the last decades of the 20 th century (e.g., Vaughan et al., 2003;Oliva et al., 2017;Turner et al., 2020), principally occurring in the northern part of the Antarctic Peninsula. Environmental changes also strongly affected the Antarctic lacustrine systems and the structure of their biotic assemblages (Quayle et al., 2002;Píšková et al., 2019;. ...
This doctoral thesis summarises and synthesises the findings of five
case studies dealing with the palaeoenvironmental evolution
of the James Ross Archipelago, Antarctic Peninsula. Through a plethora
palaeolimnological, glacial geomorphological and geochronological
methods, the Holocene evolution of Lakes Esmeralda and Monolith,
and palaeoglacier behaviour in the troughs of Prince Gustav Channel
and Croft Bay, are discerned. The absolute dating control enabled by the
use of radiocarbon, optically stimulated luminescence, and 10Be-26Al
cosmogenic isotope exposure dating methods, were crucial
for establishing the time frame of the Holocene events.
... They situated this turning point between mid-1998 and early 1999. Oliva et al. (2017) showed that this cooling trend has been most significant in the N and NE of the AP and the South Shetland Islands (SSI) (Figure 1.3), with typical summer mean temperature changes of −0.5 • C between the decades 1996−2005 and 2006−2015. Oliva et al. (2017) also analyzed the impact of this cooling trend on the cryosphere of the northern AP, including the slowdown of glacier recession, a shift to a slightly positive Surface Mass Balance (SMB) of the peripheral glaciers, and, in the SSI, also a lengthening of the snow cover duration and a thinning of the active layer of permafrost. ...
... Oliva et al. (2017) showed that this cooling trend has been most significant in the N and NE of the AP and the South Shetland Islands (SSI) (Figure 1.3), with typical summer mean temperature changes of −0.5 • C between the decades 1996−2005 and 2006−2015. Oliva et al. (2017) also analyzed the impact of this cooling trend on the cryosphere of the northern AP, including the slowdown of glacier recession, a shift to a slightly positive Surface Mass Balance (SMB) of the peripheral glaciers, and, in the SSI, also a lengthening of the snow cover duration and a thinning of the active layer of permafrost. Carrasco et al. (2021) have suggested that this cooling trend could have come to an end. ...
... Our results of mass balance close to balance agree with the warming hiatus in the Antarctic Peninsula region in the early 21st century, more significant in its northern part and the SSI (Oliva et al., 2017). In fact, our observation period of 2013-2017 overlaps with the last decade of meteorological records analyzed by these authors, for which they observed a summer average temperature change in the SSI of −0.5 • C with respect to the previous decade. ...
The glaciers on the Antarctic Peninsula (AP) play an important role in ocean dynamics, global climate, and ecology. During recent decades, the AP has become an important contributor to sea-level rise. Despite this, the ice discharge, mass balance, and total volume of the region remain unclear. Furthermore, although the glaciers in the Antarctic periphery currently contribute modestly to sea-level rise, their contribution is projected to increase substantially until the end of the 21st century. This thesis aims to develop data processing and analysis methods that allow us to generate novel updated glacier data for the Antarctic Peninsula region. This is achieved using satellite remote sensing techniques such as radar and optical images, and also numerical models to infer the ice-thickness distribution of the Antarctic Peninsula Ice Sheet (APIS), with the goal of improving ice-discharge and total ice volume estimates for this region. The fundamentals of remote sensing are presented, including techniques such as synthetic aperture radar (SAR), InSAR, DInSAR, and offset-tracking. Optical imagery and Digital Elevation Model (DEM) techniques are also presented. We then focus on glacier flow modeling, describing the governing equations (mass and momentum conservation, rheology) and approximations such as shallow ice and perfect plasticity, used to infer the ice thickness of the Antarctic Peninsula Ice Sheet (APIS). The South Shetland Islands (SSI), located north of the Antarctic Peninsula, lack a geodetic mass balance calculation for the entire archipelago. Therefore, we estimate its geodetic mass balance over the period 2013-2017. Our estimation is based on remotely-sensed multispectral and interferometric SAR data covering 96% of the glacierized areas of the islands considered in our study and 73% of the total glacierized area of the SSI. Our results show a close to balance, slightly negative average specific mass balance for the whole area of −0.106 ± 0.007 m w.e. a⁻¹, and a mass change rate of −238 ± 12 Mt a⁻¹. These results are consistent with a wider scale geodetic mass balance estimation and with glaciological mass balance measurements at SSI locations for the same study period. They are also compatible with the cooling trend observed in the region between 1998 and the mid-2010s. We computed the ice discharge from the APIS north of 70ºS for the five most widely used ice-thickness reconstructions, using a common surface velocity field and a common set of flux gates. In this way, the differences in ice discharge can be solely attributed to the differences in ice thickness at the flux gates. The total volumetric ice discharge for 2015-2017 ranges within 45-141 km³ a⁻¹, depending on the ice-thickness model, with a mean of 87 ± 44 km³ a⁻¹. The substantial differences between the ice-discharge results and a multi-model normalized root-mean-squared deviation of 0.91 for the whole data set, reveal large differences and inconsistencies between the ice-thickness models. This makes evident the scarcity of appropriate ice-thickness measurements and the difficulty of the current models to reconstruct the ice-thickness distribution in this complex region. Motivated by this uncertainty about the ice-thickness distribution, we used a finite element method to infer the ice thickness in the APIS north of 70ºS applying a two-step approach. The first step uses two different assumptions, namely, the shallow ice approximation (SIA) and the perfect plasticity (PP). The second step then uses the mass conservation equation to estimate the thickness in fast-flowing regions, with the aim of overcoming the limitations of SIA and PP near the glacier termini. Manual adjustment of glacier outlines and new ways to deal with rheological parameters along the margins provided further improvements. The application of the model at our study site resulted in a total ice volume of 28.7 ± 6.8 103 km³ and an ice discharge of 95.0 ± 14.3 km³ a⁻¹.
... A relatively short but sustained cooling period followed, spanning between the end of the 20 th century and the mid-2010s (Turner et al. 2016). This cooling mostly focused on the northern AP and the South Shetland Islands (SSI) (Oliva et al. 2017), where winter (summer) temperature decreased in the order of 1.0°C (0.5°C) per decade between the decades 1996−2005 and 2006−2015. Afterwards, a return to warming conditions has been observed (Carrasco et al. 2021). ...
... Turner et al (2016) attributed this change to a greater frequency of cold, east-to-southeasterly winds, resulting from more cyclonic conditions in the northern Weddell Sea linked to a strengthening of the mid-latitude jet, further amplified by the increased advection of sea ice towards the east coast of the northern AP due to the mentioned air circulation changes. Soon afterwards, Oliva et al. (2017) analysed the spatially-distributed temperature trends and the inter-decadal temperature variability from 1950 to 2015, using data from ten stations distributed across the AP region. The main result from their analysis was that the cooling period pointed out by Turner et al. (2016) mostly focused on the northernmost AP (north of 65 S) and the SSI, where Oliva et al. (2017) reported winter (summer) temperature decreases in the order of 1.0°C (0.5°C) per decade between the decades 1996−2005 and 2006−2015. ...
... Soon afterwards, Oliva et al. (2017) analysed the spatially-distributed temperature trends and the inter-decadal temperature variability from 1950 to 2015, using data from ten stations distributed across the AP region. The main result from their analysis was that the cooling period pointed out by Turner et al. (2016) mostly focused on the northernmost AP (north of 65 S) and the SSI, where Oliva et al. (2017) reported winter (summer) temperature decreases in the order of 1.0°C (0.5°C) per decade between the decades 1996−2005 and 2006−2015. After the mid-2010s, a return to warming conditions in the region has been observed (Carrasco et al. 2021). ...
We calculated and analysed the climatic mass balance of Hurd and Johnsons glaciers, Livingston Island, northern Antarctic Peninsula region, over the period 2002−2016. This period is nearly coincident with the transient period of sustained cooling occurred in the northern Antarctic Peninsula region in the early 21st century. A positive trend for the climatic mass balance of ~0.5-0.6 m w.e. decade-1 was observed, in parallel with a striking negative trend of the equilibrium line altitude of ~ -100-200 m decade-1, and a positive trend of the accumulation area ratio of ~3-6% decade-1. Other glaciers monitored in the South Shetland Islands and the periphery of the northernmost Antarctic Peninsula have shown a similar behavior, with the changes observed in the former being more marked.
... These studies usually ignored climatic data from 21st century and mostly concentrated on the time frame from the late 1950s to the early 2000s. Furthermore, they ignored interdecadal or shorter-term changes (Oliva et al., 2017). However, some recent reports have provided initial indications suggesting a significant slowdown in warming over the AP region since the beginning of the 21st century. ...
... However, some recent reports have provided initial indications suggesting a significant slowdown in warming over the AP region since the beginning of the 21st century. According to Oliva et al. (2017), the cooling that began in 1998/1999 was particularly notable in the northern and northeastern regions of the AP and the South Shetland Islands. It showed a moderate impact on the Orkney Islands but was not present in the southwestern part of the AP. ...
... There is an increased likelihood that the present-day expansion in the leading edge of the RIS is responsible for this drop-in temperature. Oliva et al. (2017) investigated effect of climate cooling on the Antarctic Peninsula. They observed that this cooling phenomenon had several notable effects on the cryosphere, including a deceleration in glacier recession, alterations in the surface mass gains of peripheral glaciers, and a reduction in the thickness of the active layer of permafrost on the islands in the northern Antarctic Peninsula. ...
Climate variability is thought to have an impact on the Ronne Ice Shelf (RIS), one of the largest ice shelf in Antarctica, located at the mouth of the Weddell Sea. However, investigations evaluating the impact of climate variability on the geometry (front edge) of this ice body have not yet been done. This study examines a spatial-temporal shift in the front edge of the Ronne Ice Shelf during the years 2004-2019 using an integrated approach based on remote sensing and climate data. The Moderate Resolution Imaging Spectro-radiometer (MODIS) satellite images have been used to study the changes in the ice shelf along transects drawn at a constant interval of 5 km throughout the 16-year period over the second half of the austral summer months (February to March). The study reveals that there has been net progradation of ~20 km in the front edge of the ice shelf in the sector 2 between 2004 and 2019. This progradation in the ice shelf may be attributed to draining of upper ice streams to the RIS and the decrease in temperature. Thus, the present study establishes how a combination of the use of satellite imagery and statistics can effectively be used to comprehend and quantify changes in the variability of the front edge of the ice shelf.
... In the SSI, about 100 km off the northwest Antarctic Peninsula (Figure 1a), the MAAT increased nearly 2 • C from 1968 until 2022 (Figure 1b). The MAAT is close to −2 • C at sea level [25], which makes the cryosphere very sensitive to small air temperature changes [26][27][28]. ...
... cm/year [31,32] and soil cooling as inferred from annual freezing indexes [34]. Lower summer temperatures have promoted a longer snow cover period [33,35], cooling the ground [25] Permafrost is widespread in the Antarctic Peninsula, except close to sea level in its northwestern sector [29]. Modeling of the temperature at the top of permafrost shows that the SSI have permafrost temperatures above −2 °C, but frequently, just below freezing [28,30]. ...
... cm/year [31,32] and soil cooling as inferred from annual freezing indexes [34]. Lower summer temperatures have promoted a longer snow cover period [33,35], cooling the ground [25]. ...
In the second half of the 20th century, the western Antarctic Peninsula recorded the highest mean annual air temperature rise in the Antarctic. The South Shetland Islands are located about 100 km northwest of the Antarctic Peninsula. The mean annual air temperature at sea level in this Maritime Antarctic region is close to −2 °C and, therefore, very sensitive to permafrost degradation following atmospheric warming. Among geomorphological indicators of permafrost are rock glaciers found below steep slopes as a consequence of permafrost creep, but with surficial movement also gen-erated by solifluction and shallow landslides of rock debris and finer sediments. Rock glacier surface velocity is a new essential climate variable parameter by the Global Climate Observing System, and its historical analysis allows insight into past permafrost behavior. Recovery of 1950s aerial image stereo-pairs and structure-from-motion processing, together with the analysis of QuickBird 2007 and Pleiades 2019 high-resolution satellite imagery, allowed inferring displacements of the Hurd rock glacier using compression ridge-and-furrow morphology analysis over 60 years. Displacements measured on the rock glacier surface from 1956 until 2019 were from 7.5 m to 22.5 m and surface velocity of 12 cm/year to 36 cm/year, measured on orthographic images, with combined deviation root-mean-square of 2.5 m and 2.4 m in easting and northing. The inferred surface velocity also provides a baseline reference to assess today’s displacements. The results show patterns of the Hurd rock glacier displacement velocity, which are analogous to those reported within the last decade, without being possible to assess any displacement acceleration.
... surrounded by a relatively flat area. The current MAAT on King George Islands is around − 2.1 • C (Tables 1, 2), with a recent warming rate of 0.13 • C/decade over the period 1968-2015 (Oliva et al., 2017b). The annual precipitation is around 500-1000 mm, with prevailing winter snowfall and rainfall during the summer season (van Wessem et al., 2016). ...
... Warming has been occurring with an overall MAAT increase of 0.8-3.0 • C between 1950 and 2015 (Oliva et al., 2017b;Turner et al., 2020). The Antarctic Peninsula Ice Sheet retreated from the western continental shelf break relatively rapidly after 18 ka BP, firstly in the north and subsequently the lift-off of grounded ice progressed southwards (Ó Cofaigh et al., 2014). ...
... 1.5-2.0 • C has occurred over the last 40 years in the region (Oliva et al., 2017b;Turner et al., 2020). ...
... A warming trend across the AP and SSI between 1950 and 1999 CE drove increased rates of glacier retreat, ice-shelf collapse (Meredith and King, 2005;Vaughan et al., 2003) and elevated the ELA on the SSI to greater than 200 m above present sea level (henceforth, m a.s.l.) (Falk et al., 2018). Similar to most other stations on the AP and SSI, temperature data from the Bellingshausen Station exhibit decadal scale variability, which has been linked to the El Niño Southern Oscillation (ENSO) (Oliva et al., 2017). Warming initiated approximately five years prior to El Niño in 1982-1983CE and 1997-1998 CE was followed by a cooling trend to 2015 CE and a return to a warming trend between 2015 and 2021 CE. ...
... Warming initiated approximately five years prior to El Niño in 1982-1983CE and 1997-1998 CE was followed by a cooling trend to 2015 CE and a return to a warming trend between 2015 and 2021 CE. Although a shift to a cooling trend was observed across the northern AP (NAP) between 1999 and 2015 CE, record summer temperatures have since been measured on the northeastern AP, and attributed to an enhanced Föhn effect (Oliva et al., 2017;Turner et al., 2016). ...
... Since 1957 CE, the longer-term pattern of interannual variability in the SAM has been altered by the ozone hole over Antarctica, which, combined with increased greenhouse gases and global temperature, has led to more positive SAM-like conditions, similar to the early Holocene, and enhanced the ENSO (Marshall, 2007) (Figure 7d). Increased cyclonic activity in the Drake Passage between 1996 and 2005 CE has been linked to a more poleward focussed SHW and more positive SAM, driving sea-ice poleward and increasing the advection of warm air across the NAP and SSI during winter (Marshall et al., 2017;Oliva et al., 2017). Between 2006 and 2015 CE colder winters pushed sea ice north, increasing snowfall across the NAP and doubling snow cover on some SSI islands between 2009 and 2014 CE (de Pablo et al., 2013;Oliva et al., 2017). ...
To provide insights into glacier-climate dynamics of the South Shetland Islands (SSI), NW Antarctic Peninsula, we present a new deglaciation and readvance model for the Bellingshausen Ice Cap (BIC) on Fildes Peninsula and for King George Island/Isla 25 de Mayo (KGI) ~62°S. Deglaciation on KGI began after c. 15 cal. ka BP and had progressed to within present-day limits on the Fildes Peninsula, its largest ice-free peninsula, by c. 6.6–5.3 cal. ka BP. Probability density phase analysis of chronological data constraining Holocene glacier advances on KGI revealed up to eight 95% probability ‘gaps’ during which readvances could have occurred. These are grouped into four stages – Stage 1: a readvance and marine transgression, well-constrained by field data, between c. 7.4 and 6.6 cal. ka BP; Stage 2: four probability ‘gaps’, less well-constrained by field data, between c. 5.3 and 2.2 cal. ka BP; Stage 3: a well-constrained but restricted ‘readvance’ between c. 1.7 and 1.5 cal. ka BP; Stage 4: two further minor ‘readvances’, one less well-constrained by field data between c. 1.3 and 0.7 cal. ka BP (68% probability), and a ‘final’ well-constrained ‘readvance’ after <0.7 cal. ka BP. The Stage 1 readvance occurred as colder and more negative Southern Annular Mode (SAM)-like conditions developed, and marginally stronger/poleward shifted westerly winds led to more storms and precipitation on the SSI. Readvances after c. 5.3 cal. ka BP were possibly more frequent, driven by reducing spring/summer insolation at 62°S and negative SAM-like conditions, but weaker (equatorward shifted) Westerlies over the SSI led to reduced storminess, restricting readvances within or close to present day limits. Late Holocene readvances were anti-phased with subaquatic freshwater moss layers in lake records unaffected by glaciofluvial inputs. Retreat from ‘Neoglacial’ glacier limits and the recolonisation of lakes by subaquatic freshwater moss after 1950 CE is associated with recent warming/more positive SAM-like conditions.
... The warming of the Antarctic Peninsula region has been confirmed on the basis of numerous studies especially in its western part, which shows mean annual air temperatures ranging from −2 to −4°C (Turner et al., 2020). However, atmospheric cooling was observed since the late 1990s Oliva et al., 2017), which also affected the cryosphere, including active layer and permafrost temperatures (Oliva et al., 2017;Hrbáček and Uxa, 2020). ...
... The warming of the Antarctic Peninsula region has been confirmed on the basis of numerous studies especially in its western part, which shows mean annual air temperatures ranging from −2 to −4°C (Turner et al., 2020). However, atmospheric cooling was observed since the late 1990s Oliva et al., 2017), which also affected the cryosphere, including active layer and permafrost temperatures (Oliva et al., 2017;Hrbáček and Uxa, 2020). ...
... Hrbáček et al., 2021) or active layer thinning (e.g. Ramos et al., 2017;de Pablo et al., 2017;Hrbáček and Uxa, 2020) as results of atmospheric cooling in the region Oliva et al., 2017). ...
Climate change and its impacts on sensitive polar ecosystems are relatively little studied in Antarctic regions. Permafrost and active layer changes over time in periglacial regions of the world are important indicators of climate variability. These changes (e. g. permafrost degradation, increasing of the active layer thickness) can have a significant impact on Antarctic terrestrial ecosystems. The study site (AWS-JGM) is located on the Ulu Peninsula in the north of James Ross Island. Ground temperatures at depths of 5, 50, and 75 cm have been measured at the site since 2011, while air temperature began to be measured in 2004. The main objective is to evaluate the year-to-year variability of the reconstructed temperature of the top of the permafrost table and the active layer thickness (ALT) since 2004 based on air temperature data using TTOP and Stefan models, respectively. The models were verified against direct observations from a reference period 2011-2021 showing a strong correlation of 0.95 (RMSE = 0.52) and 0.84 (RMSE = 3.54) for TTOP and Stefan models, respectively. The reconstructed average temperature of the permafrost table for the period 2004-2021 was -5.8 °C with a trend of -0.1 °C/decade, while the average air temperature reached -6.6 °C with a trend of 0.6 °C/decade. Air temperatures did not have an increasing trend throughout the period, but in the first part of the period (2004/05-2010/11) showed a decreasing tendency (-1.3 °C/decade). In the period 2011/12-2020/21, it was a warming of 1.9 °C/decade. The average modelled ALT for the period 2004-2021 reached a value of 60cm with a trend of -1.6 cm/decade. Both models were found to provide reliable results, and thus they significantly expand the information about the permafrost and ALT, which is necessary for a better understanding of their spatiotemporal variability and the impact of climate change on the cryosphere.
... (Falk et al. 2018). Similar to most other stations on the AP and SSI, temperature data from the Bellingshausen Station exhibit decadal scale variability, which has been linked to the El Niño Southern Oscillation (ENSO) (Oliva et al., 2017). Warming initiated ~5 years prior to El Niño in 1982-3 CE and 1997-8 CE was followed by a cooling trend to 2015 CE and a return to a warming trend between 2015-21 CE (Figure1E). ...
... Warming initiated ~5 years prior to El Niño in 1982-3 CE and 1997-8 CE was followed by a cooling trend to 2015 CE and a return to a warming trend between 2015-21 CE (Figure1E). The shift to a cooling trend between 1999-2015 CE has been observed across NAP, with recent record summer temperatures on the northeastern AP attributed to an enhanced fohn effect (Turner et al., 2016;Oliva et al., 2017). ...
... Between 2006-2015 CE colder winters pushed sea ice north, increasing snowfall across the NAP and doubling snow cover on some SSI islands between 2009-14 CE (Olivia et al., 2017de Pablo et al., 2017). As a result, the more northerly and low-lying SSI became colder, wetter and its glacier surface mass balance shifted to more positive mode (gaining mass) (Thomas et al., 2008;Goodwin et al., 2016;Oliva et al., 2017;Falk et al., 2018). ...
The timing of mid–late Holocene deglaciation and glacier readvances on the South Shetland Islands, northern Antarctic Peninsula has been long debated. We used a combined geomorphological, chronological, and palaeolimnological approach to develop a new readvance model for the Bellingshausen Ice Cap (BIC) on the Fildes Peninsula, King George Island/Isla 25 de Mayo, South Shetland Islands, NW Antarctic Peninsula. Results show that retreat to within present-day limits occurred by c. 6 ka, as spring/summer insolation at 62 °S peaked. Probability density analysis of new and previously published chronological data (n=80) from across Fildes Peninsula and King George Island identified up to eight probability ‘gaps’ when glacier readvances might have occurred: 1) a well-defined readvance (with a marine transgression) between c. 7.4–6.6 ka cal BP; 2–5) four possible readvances between c. 5.3–4.8 ka cal BP, 4.5–3.9 ka cal BP, 3.3–3.0 ka cal BP and/or 2.6–2.2 ka cal BP; 6) a well-defined readvance at 1.7–1.3 ka; 7–8) well-defined readvances between c. 1.3–0.7 and after <0.7 ka cal BP. Mid-late Holocene readvances of the BIC on the Fildes Peninsula were limited to within or around the current ice margin. Prior to c. 5 ka cal BP, readvances were initiated during phases of reduced global solar irradiance, with colder and more humid negative Southern Annular Mode (SAM)-like conditions. After c. 5 ka, a declining trend in insolation at 62 °S led to persistently colder/ wetter and more negative SAM-like conditions that likely drove late Holocene readvances.
... West Antarctica and the AP provide important arguments about the long-term future effects of global climate change such as surface warming and melting (Marshall et al. 2006;Steig et al. 2009;Bromwich et al., 2013;Holland et al. 2019). Since the late 1990s, a cooling period has been observed in the AP and is attributed to atmospheric teleconnections (Carrasco 2013;Turner et al. 2016;Oliva et al. 2017). The ENSO is also very important and together with the SAM modifies the climate behavior in the region. ...
... A seasonal analysis of the monthly extreme air temperature and wind components is carried out, considering the average of the months of each season or only the month with a significant trend. Reanalysis wind components in the maritime region is used in order to analyze their influences on the temperature in the study region where thermal variability has been shown to be vulnerable to warming and cooling episodes according to regional characteristics (Oliva et al. 2017). Besides MK, Sen's slope and Pettitt's approach are applied to estimating the slope of a regression line and also identifying local change-points (Tables 3, 4, and 5). ...
The west side of the Antarctic Peninsula (AP) has shown great variability since the middle of the last century characterized by warming mainly because of the oceanic and atmospheric effects such as the disintegration of floating ice and the strength of westerly winds. Here, we used two climatic databases (reanalysis from 1979 to 2020 and surface stations from 1947 to 2020) to investigate trends in extreme air temperatures and wind components in the oceanic region between 55° S and 70° S in the west (75° W) and in the east sector (45° W) and over the AP (60° W). Non-parametric statistical trend tests and extreme value approaches are used. A set of annual, monthly, and seasonal series are fitted. The extremal index is applied to measure the degree of independence of monthly excesses over a threshold considered extreme events. Increasing trends are verified in the annual and monthly temperature and wind series. The greatest trends are observed for seasonal series from reanalysis without change-point in summer and winter. Decreasing trends are observed for maximum temperature in summer and positive trends mainly for the westerly winds over the AP. But in winter, the maximum temperature shows an increasing trend also over the AP. Most of reanalysis seasonal minimum temperature and wind components as well as maximum and minimum temperatures from stations present increasing trends with change-point but tend to stability after the breakpoints. The generalized distribution (GEV) is used to fit temperatures and westerly wind between South America (SA) and north of the AP. The 100-year return levels exceed the maximum value of the maximum temperature in Esperanza and maximum westerly winds at several grid points. Pareto and Poison distributions are applied for the maximum temperatures from stations and the 100-year return levels are not exceeded. Our findings show significant positive trends for monthly wind components near the SA in the region of the westerly winds whose changes in position influence directly the SAM, which modifies the atmospheric patterns in the South Hemisphere (SH). A predominance of seasonal warming is identified, which may impact the climate with consequences not only locally but also in other regions.
... The study sites are located in the parts of Antarctic Peninsula with distinctive air temperature average (e.g. Oliva et al. 2017, Turner et al. 2020, precipitation rates (e.g. van Wessem et al. 2017, Palerme et al. 2017) and the overall soil thermal conditions (e.g. ...
... The overall occurrence of snow on Nelson and King George Islands is also suggested by the isothermal ground thermal regime prior to the zerocurtain period, which is one of the indicators of snow presence (e.g. Zhang 2005, Oliva et al. 2017. In contrast, the initial thawing on James Ross Island does not show any signs of possible snowmelt infiltration. ...
Soil moisture represents one of the crucial parameters of the terrestrial environments in Antarctica. It affects the biological abundance and also the thermal state of the soils. In this study, we present one year of volumetric water content and soil temperature measurements on James Ross Island, Nelson Island and King George Island. The volumetric water content at all sites increased with depth. The mean summer values were between 0.24 and 0.37 cm3/cm3 (James Ross Island), 0.30 and 0.40 cm3/cm3 (Nelson Island) and 0.11 and 0.36 cm3/cm3 (King George Island). We found that the freezing point of the soils was close to 0°C on Nelson Island and King George Island. We attributed the lower temperature of soil freezing around -0.5°C on James Ross Island to the site location close to the sea. Even though the sites are located in the distinctive climate zones and comprise of contrasting soil types, the only differences of moisture regime were observed the surficial layer of the studied sites.
... The Antarctic Peninsula region experienced rapid environmental changes during the 20 th century, which has been associated with increases in the air temperature observed over the same period (Turner et al, 2016). As highlighted by Gonzales & Fortuny (2018) and Oliva et al. (2017), changes in air temperature are spatially discontinuous, and the north-eastern sector of the Antarctic Peninsula has seen some of the largest increases. This spatial variability can be more acutely seen in precipitation trends (Turner et al. 2019); with drying observed in East Antarctica (Robinson et al, 2018) and increased snowfall observed over the Antarctic Ice Sheet . ...
... The study period did not cover the whole ablation period, which may extend up to 8-10 weeks, therefore the summer ablation calculated from the whole runoff/ablation period would have been higher. The reason for the relatively low ablation rate could also be that the 2013 austral summer was one of the coldest in recent decades (Oliva et al., 2017), which was also reflected in the most positive mass balance observed on Whisky Glacier and Davies Dome on a nearby James Ross Island in the period 2009-2015 (Engel et al. 2019). Therefore, we argue that runoff from the glacierized catchment measured directly by standard hydrological methods may serve as a useful proxy for the estimation of the overall ablation rate of the glacier. ...
Increasing temperatures in Antarctica have resulted in the enlargement of proglacial regions on the Antarctic Peninsula, following glacier melt. This melt has increased river activity yet direct runoff measurements remain scarce in Antarctica, despite it acting as a proxy for glacial ablation. Here, we present discharge and water temperature data from 2013 for three streams on Vega Island and discuss their relationship with air temperature. The average discharge at the largest stream was 0.523 m³s⁻¹ with a maximum of 5.510 m³s⁻¹; one of the highest recorded in Antarctica. The rivers continued to flow even when temperatures dropped to -7°C, indicating that a large proportion of the total runoff originated subglacially. This is supported by the one-day time lag between air and water temperatures. Using river discharge as a proxy, we measured 124.5 ±14.4 mm w.e. of ablation. This indirect measurement proved to be an effective tool to complement classic glaciological observations.
... Engel et al., 2012;Cook et al., 2016;Seehaus et al., 2018) and variations in atmospheric and oceanic temperatures (e.g., Vaughan et al., 2003;Ambrožová et al., 2020;Turner et al., 2020). The sensitivity and proclivity of regional climate to large oscillations is emphasised by cessation of warming after ~2000 CE (Turner et al., 2016;Oliva et al., 2017) and advances of ice shelf fronts along the eastern Antarctic Peninsula (Christie et al., 2022). Since 2016 CE, the Antarctic Peninsula experienced several air temperature extremes (Siegert et al., 2023), which might presage the return of the predicted warming trend (Carrasco et al., 2021;Clem et al., 2022) documented also on local glaciers (Stringer et al., in review). ...
... The Mid-Late Holocene Hypsithermal was followed by cooling in the Late Holocene Neoglacial Period (Čejka et al., 2020), starting ~2 ka (thousand years) BP (= before present, 1950 CE), when local glaciers advanced (e.g., Carrivick et al., 2012;Kaplan et al., 2020;Simms et al., 2021). Warming in recent centuries accelerated during the last decades of the 20th century, principally occurring in the northern part of the Antarctic Peninsula (e.g., Vaughan et al., 2003;Mulvaney et al., 2012;Oliva et al., 2017;Turner et al., 2020;Simms et al., 2021). These environmental changes also strongly affected the Antarctic lacustrine systems and the structure of their biotic assemblages (Quayle et al., 2002;Nedbalová et al., 2017b;Píšková et al., 2019;Roman et al., 2019). ...
Lentic waterbodies provide terrestrial sedimentary archives of palaeoenvironmental change in deglaciated areas of the Antarctic. Knowledge of the long-term evolution of Antarctic palaeoenvironments affords important context to the current marked impacts of climate change in the Polar regions. Here, we present a comprehensively dated, multi-proxy sedimentary record from Monolith Lake, a distal proglacial lake in one of the largest ice-free areas of the Antarctic Peninsula region. Of the two defined sedimentary units in the cores studied, the lower Unit 1 exhibits a homogeneous composition and unvarying proxy data profiles, suggesting rapid clastic deposition under uniform, ice-proximal conditions with a sedimentation rate of ∼1 mm yr−1. 14C and optically stimulated luminescence (OSL) dating bracket the deposition interval to 1.5–2.5 ka BP, with the older age being more probable when compared to independent dating of the local deglaciation. The uppermost 11 cm of the record spans the last ∼2.2 ka BP (maximum age), suggesting a markedly decreased sedimentation rate of ∼0.05 mm yr−1 within Unit 2. Whereas Unit 1 shows only scarce evidence of biological activity, Unit 2 provides an uninterrupted record of diatoms (with 29 species recorded) and faunal subfossils, including the fairy shrimp Branchinecta gaini. Concentrations of organically-derived elements, as well as diatoms and faunal remains, are consistent, implying a gradual increase in lake productivity. These results provide an example of long-term Antarctic ‘greening’ (i.e. increasing organic productivity in terrestrial habitats) from a palaeolimnological perspective. The boundary between Units 1 and 2, therefore, marks the timing of local deglaciation at the final stages of a period of negative glacier mass balance, i.e. the Mid-Late Holocene Hypsithermal. Subsequent Neoglacial cooling is evidenced by the abated influence of glacial meltwater streams and turbidity decline linked to reduced glacier runoff, although most proxy responses mirror the natural proglacial lake ontogeny.
... This has resulted in an increase of 2.8 • C in the MAAT between 1951 and 2000 (Bozkurt et al., 2021). The warming trend was interrupted by a short cooling period from 1999 to 2015 (Bozkurt et al., 2021;Jones et al., 2019;Oliva et al., 2017;Turner et al., 2020), but since then the warming returned (Jones et al., 2019). Permafrost in the WAP is widespread but absent at sea-level from the South Shetlands to the Palmer Archipelago, except in specific settings (Vieira et al., 2010;Bockheim et al., 2013), and permafrost temperatures are close to − 2 to − 1 • C, resulting in a high sensitivity to small climate fluctuations (Obu et al., 2020). ...
... The mean annual temperature is − 2.3 °C and the summer is characterized by above-zero temperatures. There are frequent and usually strong winds, with prevailing directions from the north, northwest, west, and southeast (Oliva et al. 2017). The Fildes Peninsula's geologic formation is a complex of igneous rocks, mainly andesites, basalts, and various tuffs. ...
Research in Antarctica is of great importance for understanding the Earth’s climate system and the processes that drive it. This study evaluated the spatial distribution of glacial sediment properties on the Bellingshausen Dome or Collins Ice Cap (King George Island, Antarctica). The particle-size distribution, pH H2O, total organic carbon (TOC), mobile forms of ammonium nitrogen (N–NH4), potassium (K2O), and phosphorus (P2O5) were measured and then spatially modelled using regression kriging (RK) and ordinary kriging (OK) approaches. The terrain attributes (elevation, aspect, slope) derived from a digital elevation model with 10-m spatial resolution and distance from a coast were used as explanatory variables. Multiple linear regression models were fitted to describe the relationships between the covariates and properties. The performance of the models was evaluated by the mean absolute error (MAE), root mean square error (RMSE), coefficient of determination (R2), and Nash–Sutcliffe efficiency coefficient (NSE) indices. Overall, model performance statistics showed that RK models performed better than OK and the spatial patterns of some properties were closely related to the character of the glacier topography. Thus, the application of the RK method in combination with auxiliary environmental covariates improved the accuracy of spatial prediction.
... Presumably, the elevated SSS might be due to cooling effects in summer. Contrary to the international warming trend, it was currently reported that cooling has occurred during the summer in WAP (Oliva et al., 2017;Turner et al., 2016). Our raw data also confirmed the tendency of decrease in summer temperature. ...
... The total area of Horseshoe Island is 60 km 2 , and 66% of the island is made up of glaciers or semiperennial ice and snow. As a result of meteorological measurements at the Rothera (1977Rothera ( -2015 and San Martin (1985Martin ( -2015 stations, which are close to Horseshoe Island, it was observed that the annual average air temperatures are -4.3 and -4.6 °C, respectively (Oliva et al., 2017). ...
... A pronounced rise in the air temperature along the AP was reported in the 20th century (Turner et al., 2016). However, since the turn of the millennia, a cooling trend has been observed (Oliva et al., 2017;Turner et al., 2016). Recent analysis suggests an end to the intermediate cooling and the return of a temperature increase (Carrasco et al., 2021). ...
Some of the highest specific mass change rates in Antarctica are reported for the Antarctic Peninsula. However, the existing estimates for the northern Antarctic Peninsula (<70∘ S) are either spatially limited or are affected by considerable uncertainties. The complex topography, frequent cloud cover, limitations in ice thickness information, boundary effects, and uncertain glacial–isostatic adjustment estimates affect the ice sheet mass change estimates using altimetry, gravimetry, or the input-output method. Within this study, the first assessment of the geodetic mass balance throughout the ice sheet of the northern Antarctic Peninsula is carried out employing bi-static synthetic aperture radar (SAR) data from the TanDEM-X satellite mission. Repeat coverages from the austral winters of 2013 and 2017 are employed. Overall, coverage of 96.4 % of the study area by surface elevation change measurements and a total mass budget of -24.1±2.8 Gt a−1 are revealed. The spatial distribution of the surface elevation and mass changes points out that the former ice shelf tributary glaciers of the Prince Gustav Channel, Larsen A and B, and Wordie ice shelves are the hotspots of ice loss in the study area and highlights the long-lasting dynamic glacier adjustments after the ice shelf break-up events. The highest mass change rate is revealed for the Airy–Seller–Fleming glacier system at -4.9±0.6 Gt a−1, and the highest average surface elevation change rate of -2.30±0.03 m a−1 is observed at Drygalski Glacier. The comparison of the ice mass budget with anomalies in the climatic mass balance indicates, that for wide parts of the southern section of the study area, the mass changes can be partly attributed to changes in the climatic mass balance. However, imbalanced high ice discharge drives the overall ice loss. The previously reported connection between mid-ocean warming along the southern section of the west coast and increased frontal glacier recession does not repeat in the pattern of the observed glacier mass losses, excluding in Wordie Bay. The obtained results provide information on ice surface elevation and mass changes for the entire northern Antarctic Peninsula on unprecedented spatially detailed scales and with high precision and will be beneficial for subsequent analysis and modeling.
... The Antarctic Peninsula is one of the most rapidly warming regions on Earth, with an observed maximum rate of~0.5°C per decade since 1950 29 , although some studies suggest that this warming has momentarily declined or that a cooling has been occurring since the late 1990s [30][31][32] . Higher temperatures are accompanied by rapid changes in the cryosphere and ecosystems of the Antarctic Peninsula, such as: (1) accelerated disintegration of glaciers, with about 52% of the glaciers showing retreat and only about 9% advancing during 1991-2015 33 ; (2) reduction in seasonal sea ice extent, with the extent of summer sea ice in the Weddell Sea dropping to a near-record level in the satellite era in 2016/17 [34][35][36] . ...
Temporal and spatial variations in sea ice coverage at high Northern Hemisphere latitudes have been shown to affect the photodegradation of methylmercury in seawater and the mercury isotope signatures in biological samples, suggesting the potential of mercury isotopes to reconstruct sea ice variability. Here we study the mercury isotopic composition of a 1500-year sediment profile strongly affected by seal activities on the Fildes Peninsula, King George Island, Antarctic Peninsula. The mass independent isotope fractionation of mercury (represented by Δ¹⁹⁹Hg) in sediments dominated by seal feces input reflects the Δ¹⁹⁹Hg of marine methylmercury before entering the food web, documenting the changes in the degree of photodemethylation. We found much higher Δ¹⁹⁹Hg in sediments deposited during a warm period (~700-1000 years ago), suggesting that reduced sea ice promoted greater photodemethylation. Thus, this study demonstrates the modulation of methylmercury photodegradation by sea ice in the Antarctic, and that mercury isotopes can record historical sea ice changes.
... A decrease in large-cell diatoms, increases in cryptophytes that are less suitable for grazing by Antarctic krill Euphausia superba (hereafter 'krill') (Haberman et al. 2003) and the concurrent decrease in the sea ice extent negatively affect krill abundance (Massom & Stammerjohn 2010). Current warming seems to be more evident in the southwest AP region, while the north/north-east of the AP and South Shetland Islands switched from a warming trend between the late 1970s and 1990s to cooling between the early 2000s and mid 2010s (Oliva et al. 2017). Positive relationships between krill abundance and the cold La Niña (El Niño−Southern Oscillation [ENSO] negative phase event) (Loeb & Santora 2015) and negative relationships between krill abundance and Southern Annular Mode (SAM) phases (Atkinson et al. 2019) have been recorded. ...
... In addition, in 1970, the volume of excavated ash was not totally computed with these cartographic products. In fact, the 2020 orthographic mosaic and the REMA digital elevation model register the height of an alluvial fan that completely fills and covers the 100 m depth and 300 m diameter crater of 1970 on land [31], perhaps favoured in recent years by the rise in mean annual atmospheric temperature and snowfall [53]. ...
Aerial frames and satellite imagery are widely recognized data sources from which to produce maps. For volcanoes, maps enable the quantification of erupted ash and the destruction caused.The last eruptive sequence on Deception Island was endured from 1967 to 1970. Analogue maps were produced via classical photogrammetric methods with a high degree of human intervention
mainly to analyse the volcanic-centres areas only. However, historical aerial frames cover the whole of Deception Island. Structure from motion photogrammetry, a near-automated compilation of digital image processing strategies, minimizes the degree of human intervention to produce orthographic mosaics and digital elevation models from digital aerial frames. Orthographic mosaics were produced from historical aerial frames of 1956 and 1968, and a Kompsat-3 image of 2020. Their shared rootmean-square deviation was 1.8 m and 1.7 m in easting and northing, respectively, at ground control points measured with phase-differential global navigation satellite systems. The digital elevation models were processed with a root-mean-square deviation of 2.3 m and 3.6 m from 1956 and 1968 aerial frames, respectively. As the first application, erupted ashfall and the subsequent destruction,
mainly at the former Chilean and British bases, were identified, and the volume of erupted ash was assessed to be over 0.16 km3 within the area mapped by these new digital cartographic products.
... A pronounced rise in the air temperature along the AP was reported in the 20th century (Turner et al., 2016). However, since the turn of the millennia a cooling trend was observed (Oliva et al., 2017;Turner et al., 2016). gravimetry, input-output methods), the reported values are affected by considerable uncertainties. ...
Some of the highest specific mass change rates in Antarctica are reported for the Antarctic Peninsula. However, the existing estimates for the northern Antarctic Peninsula (< 70° S) are either spatially limited or are affected by considerable uncertainties. The complex topography, frequent cloud cover, limitations in ice thickness information, boundary effects, and uncertain glacial-isostatic adjustment estimates affect the ice sheet mass change estimates using altimetry, gravimetry, or the input-output method. Within this study, the first assessment of the geodetic mass balance throughout the ice sheet of the northern Antarctic Peninsula is carried out employing bi-static SAR data from the TanDEM-X satellite mission. Repeat coverages from austral-winters 2013 and 2017 are employed. An overall coverage of 96.4 % of the study area by surface elevation change measurements and a total mass budget of −24.1 ± 2.8 Gt/a is revealed. The spatial distribution of the surface elevation and mass changes points out, that the former ice shelf tributary glaciers of the Prince-Gustav-Channel, Larsen-A&B, and Wordie ice shelves are the hotpots of ice loss in the study area, and highlights the long-lasting dynamic glacier adjustments after the ice shelf break-up events. The highest mass change rate is revealed for the Airy-Seller-Fleming glacier system of −4.9 ± 0.6 Gt/a and the highest average surface elevation change rate of −2.30 ± 0.03 m/a is observed at Drygalski Glacier. The comparison of the ice mass budget with anomalies in the climatic mass balance indicates, that for wide parts of the southern section of the study area, the mass changes can be partly attributed to changes in the climatic mass balance. However, imbalanced high ice discharge drives the overall ice loss. The previously reported connection between mid-ocean warming along the southern section of the west coast and increased frontal glacier recession does not repeat in the pattern of the observed glacier mass losses, excluding Wordie Bay. The obtained results provide information on ice surface elevation and mass changes for the entire northern Antarctic Peninsula on unprecedented spatially detailed scales and high precision and will be beneficial for subsequent analysis and modeling.
... In addition, in the eastern sector, the sea surface salinity has been decreasing due to the disintegration and thinning of the ice shelves (Paolo et al., 2015;Pritchard et al., 2012). Moreover, although atmospheric warming has already exceeded 1.5°C over the second half of the 20th century (Turner et al., 2005), air temperature trends have markedly reversed over the first two decades of the 21st century in the NAP (see inset in Figure 1; Clem et al., 2020;Oliva et al., 2017;Turner et al., 2016). This reversal is mostly explained by regional wind patterns coupled with an inversion of the Interdecadal Pacific Oscillation (Stammerjohn & Scambos, 2020). ...
The western Antarctic Peninsula (WAP) is a climatically sensitive region where foundational changes at the basis of the food web have been recorded; cryptophytes are gradually outgrowing diatoms together with a decreased size spectrum of the phytoplankton community. Based on a 11-year (2008-2018) in-situ dataset, we demonstrate a strong coupling between biomass accumulation of cryptophytes, summer upper ocean stability, and the mixed layer depth. Our results shed light on the environmental conditions favoring the cryptophyte success in coastal regions of the WAP, especially during situations of shallower mixed layers associated with lower diatom biomass, which evidences a clear competition or niche segregation between diatoms and cryptophytes. We also unravel the cryptophyte photo-physiological niche by exploring its capacity to thrive under high light stress normally found in confined stratified upper layers. Such conditions are becoming more frequent in the Antarctic coastal waters and will likely have significant future implications at various levels of the marine food web. The competitive advantage of cryptophytes in environments with significant light level fluctuations was supported by laboratory experiments that revealed a high flexibility of cryptophytes to grow in different light conditions driven by a fast photo-regulating response. All tested physiological parameters support the hypothesis that cryptophytes are highly flexible regarding their growing light conditions and extremely efficient in rapidly photo-regulating changes to environmental light levels. This plasticity would give them a competitive advantage in exploiting an ecological niche where light levels fluctuate quickly. These findings provide new insights on niche separation between diatoms and cryptophytes, which is vital for a thorough understanding of the WAP marine ecosystem.
... The region has seen the greatest warming trends recorded in Antarctica over the past 60 years (Turner et al., 2014), with a mean annual air temperature of -2.2°C and precipitation ranging between 350 and 1000 mm year -1 (Simas et al., 2015). The mean summer air temperature is 1.2°C (Oliva, 2017) and is >0°C for up to 4 months, which means that water will be available for biological activity, chemical and physical weathering and hydrological and geomorphological processes (Michel et al., 2014a;Simas et al., 2015). A predominance of summer temperatures above freezing within the Maritime Antarctic region, with frequent freeze-thaw cycles, produces cryoclastic weathering and cryoturbation in these icefree areas (Navas et al., 2008;Balks et al., 2013). ...
The environmental conditions in Maritime Antarctica are more favorable to soil development than in continental areas, which is reflected in the content and type of clay minerals present. In this context, soil clay minerals of Fildes Peninsula, South Shetland Islands were studied with the aim of relating them to periglacial and paraglacial processes as possible indicators of initial pedogenic processes. In this work, textural, mineralogical and crystallochemical characterization of clay minerals as well as chemical and physical soil analyses were carried out. The soil samples represented various surface cover types present on Fildes Peninsula. All samples were composed mainly of clay minerals, plagioclase, quartz and minor zeolites and pyroxene. The clay mineral content was very variable and reached up to 63% w/w. The clay minerals present are mainly smectite, vermiculite, chlorite and minor kaolinite, mica, corrensite and interstratified illite–smectite, with smectite and vermiculite dominating in almost all of the samples. The primary minerals display chemical alteration, and smectite formed by alteration of plagioclase. The clay mineral types were related to the parent material, which was affected by low-grade metamorphism and hydrothermal alteration that transformed biotite and chlorite into vermiculite via interstratified chlorite–vermiculite. Furthermore, this process and/or ongoing surface weathering transformed vermiculite into smectite. The genetic relationship observed between vermiculite and smectite suggests progressive alteration and transformation into a phase with intermediate composition between vermiculite and smectite. Therefore, vermiculite could be at least in part the smectite precursor. Samples closer to the current Collins Glacier front are composed mainly of vermiculite, with the greatest chemical variation occurring where the soils were developed from a mixture of initially glacially transported volcanic rocks through periglacial and fluvial processes. The clay minerals from the centre and south of Fildes Peninsula are mixtures of montmorillonite and vermiculite, as well as of chlorite and corrensite in various proportions. The clay minerals in soils developed on the west coast are a mixture of Fe-rich montmorillonite and vermiculite.
... Studies mainly focus on ice-free areas and are generally related to the comparison of sea and continental conditions, changes in summer ground surface temperature (SGST) and the thickness of the active layer in relation to changes in air temperature, the role of radiation in summer and the thickness and duration of snow cover, lithology, and the occurrence of vegetation (e.g., [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] ). These studies also allow us to determine the necessary threshold conditions for the detection of life and its adaptation mechanisms (e.g., [28][29][30], which may constitute an analogy for the search for appropriate conditions on other icy worlds (e.g., 31,32 ). ...
The Antarctic continent is a crucial area for ultimate determination of permafrost extent on Earth, and its solution depends on the theoretical assumptions adopted. In fact, it ranges from 0.022 × 106 to 14 × 106 km2. This level of inaccuracy is unprecedented in the Earth sciences. The novelty of the present study consists in determining the extent of Antarctic permafrost not based exclusively on empirical studies but on universal criteria resulting from the definition of permafrost as the thermal state of the lithosphere, which was applied for the first time to this continent. The area covered by permafrost in Antarctica is ca. 13.9 million km2, that is its entire surface. This result was also made possible due to the first clear determination of the boundaries and area of the continent. The Antarctic area includes (a) rocky subsurface with (b) continental ice‐sheets and (c) shelf glaciers, which, due to their terrigenous origin and belonging to the lithosphere, belongs to the continent in the same way. Antarctica is covered by continuous permafrost, either in a frozen or in a cryotic state. This also significantly influences delimitation of the global extent of permafrost, which can therefore be defined much more accurately. The proposed ice reclassification and its transfer from the hydrosphere to the lithosphere will allow the uniform treatment of ice in the Earth sciences, both on Earth and on other celestial bodies.
We have characterized the magnitude and spatial extent of observed regional and inter-regional air temperature trends and warming extremes across Antarctica. Prior studies have used localized observational records to analyze air temperature trends across distinct geographical regions, leaving local and inter-regional variations to be undetected. Using the high-resolution temperature product AntAir ICE, air temperature trends and extreme warming events during austral summers were identified across Antarctica for the period 2003-2021. Unsupervised clustering was applied to austral summer and annual mean air temperature trends to divide Antarctica into 12 regions exhibiting similarity in temperature trends. Our results show a significant annual mean cooling trend of - 0.12 °C/Yr for the terrestrial Antarctic Peninsula, and an austral summer (annual) warming trend of + 0.08°C/Yr (+0.07 °C/Yr) in the Ross Sea region’s Victoria Land and Transantarctic Mountains. The spatial extent of each of the 12 clusters’ extreme air temperature events was mapped revealing that West Antarctica has spatially confined events, while East Antarctica events are widespread. ERA5 data indicates that West Antarctica’s extreme air temperature events are associated with consistent meridional atmospheric flows. Local to regional extreme warming events in East Antarctica are associated with inland high-pressure systems, which enhance katabatic winds. Localized warming events around complex coastal geographies were detected and appear to be related to mesoscale wind systems such as foehn but require further investigation using mesoscale numerical weather models. This work highlights the necessity for ongoing and new monitoring in regions where critical ecological and physical thresholds are being surpassed.
The geochemistry of lake sediments provides valuable information on environmental conditions and geochemical processes in polar regions. To characterize geochemical composition and to analyse weathering and provenance, 26 lakes located in six islands of the South Shetland Islands (SSI) and James Ross Archipelago (JRA) were analysed. Regarding major composition, the studied lake sediments correspond to ferruginous mudstones and to a lesser extent to mudstones. The weathering indices indicate incipient chemical alteration (Chemical Index of Alteration = 52.6; Plagioclase Index of Alteration = 57.6). The La-Th-Sc plot shows different provenance signatures. SSI lake sediments correspond to oceanic island arcs, whereas those of JRA denote a signal of continental arcs with mixed sources. In James Ross Island lake sediments are of continental arcs (inland lakes), oceanic island arcs (coastal lakes) and a middle signature (foreland lakes). Multi-elemental analysis indicates that the sediments are enriched from regional basalts in Ba, Rb, Th, Cs and U (typical of silica-rich rocks) and depleted in Cr and Co due to mafic mineral weathering. The geochemical signals identified by principal component analysis enable us to group the sediments according to the studied islands and their geomorphological characteristics. This study underlines the importance of knowing the geochemical background levels in pristine lake sediments to evaluate potential future anthropogenic effects.
Underwater imagery survey was conducted to address changes in Antarctic benthic megafauna communities by recent glacial retreat in Marian Cove, where the distance from the glacier was proportional to retreat period. Benthic megafauna communities showed lesser variation due to frequent ice-scouring at 10 m than deeper seabed. At deep seabed, where glacier impacts decreased, benthic megafauna was scarce right in front of the glacier, but near the glacier (~ 10 years after seabed exposure), the density peaked (116 ind. m − 2 ) with pioneer species. At the outermost site, pioneer species were extremely limited (9 ind. m − 2 ) and late-successional species were abundant (21 ind. m − 2 ). Taxonomic and functional diversities peaked near the glacier and outermost site, respectively, indicating different mechanisms of structural and functional change after glacial retreat. This study showed a four-step successional process of benthic megafauna communities after glacial retreat in Antarctic nearshore: high disturbance, colonization, transition, and maturing stages.
The Antarctic Peninsula (AP) has displayed a propensity for persistent blocking ridges and anticyclonic conditions, particularly during recent summertime extreme weather events. This study investigates atmospheric blocking patterns over the AP through historical (1981–2010) and future (2071–2100, SSP5–8.5) periods using ERA5 reanalysis and six CMIP6 models, including multi-member realizations from two models totaling ten simulations. We focus particularly on 500 hPa geopotential height (Z500) and near-surface air temperature (T2m) anomalies. The historical analysis highlights significant differences between the CMIP6 models and ERA5 reanalysis, especially in the austral winter, with EC-Earth3 and INM-CM4 models matching closest with the ERA5. Future projections show that while the northern AP and the Drake Passage largely do not exhibit a clear trend towards increased blocking, there are exceptions. The EC-Earth3 model predicts more blocking–like conditions northwest of the AP in summer and a pronounced ridge over the Bellingshausen Sea in winter, indicating a potential increase in blocking events. The INM-CM4 model projects a minor increase in summer Z500 heights off the western and southern AP, without clear blocking patterns over the AP, and negligible winter changes. Localized intensification is noted in the northern parts of the blocking domain and southern AP during extreme blocking conditions. These variations are mirrored in T2m anomalies, suggesting warming in the northern and southern sections of AP but little change elsewhere. The results of this study underscore the need to more accurately capture complex blocking mechanisms and their impacts on regional climate patterns around the AP. We also suggest employing refined blocking definitions and incorporating a broader range of climate models to enhance our understanding of blocking patterns and their impacts in a changing climate.
Las playas levantadas constituyen una de las mejores evidencias geomorfológicas que atestiguan el cambio relativo del nivel del mar ligado al retroceso de los glaciares desde la última glaciación. En las Islas Shetland del Sur (Antártida marítima), tales morfologías resultan especialmente abundantes, habiendo sido estudiadas en diferentes épocas, usando distintos métodos y a través de distintas perspectivas. El objetivo general de este trabajo es buscar y clasificar la producción científica sobre las playas levantadas en las Islas Shetland del Sur. Para ello, se exploraron los principales repositorios de publicaciones científicas obteniendo una lista definitiva de 65 trabajos que integran el conocimiento general adquirido desde la década de 1960 hasta la actualidad. Durante este período, los estudios geomorfológicos son los más frecuentes, alcanzando un máximo en la década de 2010, seguidos por investigaciones que emplean métodos geocronológicos para datar las playas levantadas. En la década de 2000 aumentó la cantidad de datos y registros, reflejado en la publicación de artículos de revisión. En la última década (2010-2019), los trabajos muestran un enfoque más multidisciplinario, integrando diversas técnicas de datación, incluyendo el ambiente periglaciar y la teledetección. Se concluye que se ha recopilado una cantidad significativa de conocimiento y datos científicos sobre las playas levantadas en las Islas Shetland del Sur, utilizando diversos enfoques, métodos y análisis.
Temperature analysis is of special interest in polar areas because temperature is an essential variable in the energy exchange between the Earth’s surface and atmosphere. Although land surface temperature (LST) obtained using satellites and air temperature (Ta) have different physical meanings and are measured with different techniques, LST has often been successfully employed to estimate Ta. For this reason, in this work, we estimated Ta from LST MODIS collection 6 (C6) and used other predictor variables. Daily mean Ta was calculated from Spanish State Meteorological Agency (AEMET) stations data on the Livingston and Deception Islands, and from the PERMASNOW project stations on Livingston Island; both islands being part of the South Shetland Islands (SSI) archipelago. In relation to our previous work carried out in the study area with collection 5 (C5) data, we obtained higher R2 values (R2CV = 0.8, in the unique model with Terra daytime data) and lower errors (RMSECV = 2.2 °C, MAECV = 1.6 °C). We corroborated significant improvements in MODIS C6 LST data. We analyzed emissivity as a possible factor of discrepancies between C5 and C6, but we did not find conclusive results, therefore we could not affirm that emissivity is the factor that causes differences between one collection and another. The results obtained with the applied filters indicated that MODIS data can be used to study Ta in the area, as these filters contribute to the reduction of uncertainties in the modeling of Ta from satellites.
Glaciers cover 132 900 km ² around the Antarctic Ice Sheet, but few are subject to annual mass-balance measurements. Lookalike Glacier and Davies Dome on James Ross Island have been monitored since 2009, providing the third longest mass-balance record for the northern Antarctic Peninsula. These glaciers had a balanced mass budget over the period 2009/10–2014/15 but started to lose their mass thereafter. Between 2014/15 and 2020/21, mass change rates were −0.15 ± 0.13 and −0.26 ± 0.11 m w.e. a ⁻¹ for Lookalike Glacier and Davies Dome, respectively. The mean equilibrium-line altitudes over this period at Lookalike Glacier (362 ± 18 m a.s.l.) and Davies Dome (>427 ± 22 m a.s.l.) are 51 and >34 m higher compared to the previous 6-year period. The mean accumulation area ratio values determined for the period 2014/15–2020/21 are lower than the balanced-budget ratio indicating that glaciers are out of balance with the current climate. The data confirm the transition from positive to negative mass-balance periods around 2014/15, which is attributed to the change in air temperature trends. The mean summer temperature increased by 0.9°C between the periods 2009/10–2014/15 and 2015/16–2020/21 and melt-season temperatures became predominantly positive.
Using data from SCAR observations, ERA5 reanalysis, and regional climate modelsimulations (RACMO), we examined the influence of large- and regional-scale climateforcing on temperature and precipitation variations in the South Shetland Islands (SSI).Specifically, we focused on understanding how regional climate indices influence thetemporal variability of temperature and precipitation on the SSI. Our findings indicatethat both large- and regional-scale climate indices significantly impact the interannualand seasonal temperature variability in the SSI. For instance, the Amundsen Sea Low,characterised by low-pressure systems over the Amundsen Sea, and sea ice extent in thenorthwestern part of the Weddell Sea, exert a strong influence on temperature variability(r from -0.64 to -0.87; p < 0.05). In contrast, precipitation variability in this region isprimarily controlled by regional climatic indices. Particularly, anomalies in atmosphericand surface pressure over the Drake Passage region strongly regulate the interannualvariability of precipitation in the SSI (r from -0.46 to -0.70; p < 0.05). Large-scale climaticindices demonstrate low but statistically significant correlations, including the SouthernAnnular Mode and deep convection in the central tropical Pacific. Given the importanceof temperature and precipitation in the glacier changes, we recommend assessing theimpact of the Drake region on SSI glaciers.
The present article objective is to determine the net mass balance of the glacier Znosko for periods 2018-2019 and 2019-2020. It is situated on King George Island which belongs to the groups Shetland of the South, Antarctic Peninsula region. For this objective, during February 2018 a net of 19 stakes (which were controlled once during February 2019 and 2020) were installed on the glacier ablation zone, drilling in the accumulation zone and about flights using unmanned aerial vehicles (UAV) to control the glacier zone and geomorphological changes. For the year 2020, it was determined a glacier area of 1.71 ± 0.02 km2, moreover, using five different methods of interpolation, it was obtained on average, as a result, a specific net balance of -590.7 ± 46.6 mm w.e (in water equivalent) for 2018-2019 and -686.7 ± 28.2 mm w.e for 2019-2020, being the ELA altitude 146.5 ± 18.2 m and 144.2 ± 8.3 m respectively. The two consecutive years represent negative net mass balances which are in accordance with other similar studies on this region, also glacier data were obtained on a zone that is characterized by its difficult access.
We analyze the internal structure of two polythermal glaciers, Hurd and Johnsons, located on Livingston Island, Antarctica, using 200 and 750 MHz GPR data collected in 2003/04, 2008/09 and 2016/17 field campaigns. Based on the different permittivities of snow and ice, we determined the thickness distribution of the end-of winter snow cover and of the cold ice layer. Their knowledge is fundamental for mass balance and glacier dynamics studies due to the different densities and rheological properties of such media. The average measured thicknesses for the snow and cold ice layers (the latter including the snow layer) were of 1.44 ± 0.09 and 29.1 ± 1.5 m, and their corresponding maxima were of 2.45 ± 0.21 and 80.8 ± 2.5 m. GPR snow profiling allowed for extension of the coverage of the snow thickness survey, but added little information to that supplied by snow pits, stake readings and manual snow probing, because of the multiplicity of reflections within the seasonal snowpack caused by internal ice layers and lenses. The polythermal structure determined for Hurd Glacier fits into the so-called Scandinavian type, seldom reported for the Antarctic region.
This study investigates the transient snowline (TSL) altitude for summer 2020, as well as glacial area loss in King George Island Icefields since 1988 using Sentinel-1 and 2 and Landsat Thematic Mapper (TM) imagery. Trends and anomalies in atmospheric temperature, U-wind, and V-wind were examined using ERA5 solutions. Results show the wet-snow zone corresponds to values of ≤ -13dB, and 44.3% of the glacial area is located above the TSL (≥ 300 m). Glacial area for 2020 is 999.95 km², and losses in the period represent 104.9 km² (error <1%) - a retreat of 3.17 km² / year. Glaciers in Keller Peninsula and Bellingshausen Dome lost the most area (28% and 17%, respectively) and did not have a TSL in 2020; followed by Warszawa (15%), Kraków (13%), and Eastern (10%), where the TSL was verified. Percentage area loss values increased with decreases in dimensions, area above TSL, and maximum elevation. Calving glaciers with ice-flow toward deeper and steeper submarine sectors (Bransfield Strait) exhibited greater glacier variations. The trend in warming atmospheric temperature was greater in the Bransfield Strait than in the Drake Passage. TSL and retreat difference between glaciers were influenced by climatic and ocean input, as well as multiple environmental factors.
The Antarctic Peninsula Ice Sheet (APIS) has become a significant contributor to sea-level rise over recent decades. Accurately estimating the ice discharge from the outlet glaciers of the APIS is crucial to quantify the mass balance of the Antarctic Peninsula. We here compute the ice discharge from the outlet glaciers of the APIS north of 70 ${^\circ }$ S for the five most widely used ice-thickness reconstructions, using a common surface velocity field and a common set of flux gates, so the differences in ice discharge can be solely attributed to the differences in ice thickness at the flux gates. The total volumetric ice discharge for 2015–2017 ranges within 45–141 km ³ a ⁻¹ , depending on the ice-thickness model, with a mean of 87 ± 44 km ³ a ⁻¹ . The substantial differences between the ice-discharge results, and a multi-model normalized root-mean-squared deviation of 0.91 for the whole data set, reveal large differences and inconsistencies between the ice-thickness models, giving an indication of the large uncertainty in the current ice-discharge estimates for the APIS. This manifests a fundamental problem of the region: the scarcity of appropriate ice-thickness measurements and the difficulty of the current models to reconstruct the ice-thickness distribution in this complex region.
The absence of vegetation in most ice‐free areas of Antarctica makes the soil surface very sensitive to atmosphere dynamics, especially in the western sector of the Antarctic Peninsula, an area within the limits of the permafrost zone. To evaluate the possible effects of regional warming on frozen soils, we conducted an analysis of ground surface temperatures (GSTs) from 2007 to 2021 from different monitoring sites in Livingston and Deception islands (South Shetlands archipelago, Antarctica). The analysis of the interannual evolution of the GST and their daily regimes and the freezing and thawing indexes reveals that climate change is showing impacts on seasonal and perennially frozen soils. Freezing Degree Days (FDD) have decreased while Thawing Degree Day (TDD) have increased during the study period, resulting in a balance that is already positive at the sites at lower elevations. Daily freeze–thaw cycles have been rare and absent since 2014. Meanwhile, the most common thermal regimes are purely frozen – F1 (daily temperatures < = −0.5°C), isothermal – IS (ranging between −0.5°C to +0.5°C), and purely thawed – T1 (> = +0.5°C). A decrease in F1 days has been observed, while the IS and T1 days increased by about 60 days between 2007 and 2021. The annual number of days with snow cover increased between 2009 and 2014 and decreased since then. The GST and the daily thermal regimes evolution point to general heating, which may be indicative of the degradation of the frozen soils in the study area.
The Lange glacier is an outlet glacier situated in the Admiralty Bay, King George Island, Peninsula Antarctica. It retreated about 1 km since the 1950s. Although recent observations do not show any significant change at the ice-ocean margin, it is not clear whether this glacier has reached a new steady state or whether it is still adjusting to new climate conditions. By combining a three-dimensional glacier model with satellite and in-situ datasets, we investigate the sensitivity of Lange glacier to perturbations in flow rate factor, friction coefficient, surface mass balance, and calving front position. The (time-dependent) perturbation experiments show that the glacier is more sensitive to changes in surface mass balance and in flow rate factor. These results suggest that the climate variability of this region plays an important role on the glacier's dynamics, and that measurements of englacial temperature will improve the reliability of future modeling efforts. Our model shows that the position of the ice front exerts a strong control on the glacier flux. In our time-dependent simulation, the impacts of the observed front retreat on the glacier's dynamics persist beyond the present date. This suggests that Lange is likely still adjusting to past perturbations at its terminus.
The paper aims to reconstruct the fluctuations of Dobrowolski Glacier, a tidewater glacier located in the inner position of the Admiralty Bay (King George Island, Antarctica), from the Little Ice Age (1400-1700) until the present. Measurements of the glacier’s area and length were based on multitemporal satellite imagery and submarine glacial landforms. The glacier surface area variations between the Little Ice Age and 2014 A.D were estimated. Morainic banks and paleoglacial reconstructions provided evidence of fluctuations in the surface area of the glacier between PIG and 2014 AD. Therefore, four stages of analysis were established: Stage I (Part I) (1400 to 1700), Stage I (Part II) (1700 until the mid-20th century), Stage II (mid-20th century until the 1980s), Stage III (1980 to 2000), and Stage IV (2000 to 2020). The climate during the Little Ice Age triggered the last major glacial advance, and their grounding line position was recorded by an external and prominent morainic bank. After the major glacial advance position of the grounding line, the ice-margin has undergone higher retreat rates (stage I) as response to the warming trend and the loss of anchoring point. The stage II (Unit B) is recorded by distal and discontinuous morainal ridges and glacial lineations formed in the context of an active ice flow at a deeper point in the fjord. During stage III (Unit C) glacial lineations and steep slopes occur, while landforms are less preserved, revealing a fast shrinkage phase. Stage IV is characterized by discontinuous morainic ridges (Unit D), when the glacier presents the highest annual glacial area loss. Currently, the accelerated shrinkage may be linked to the loss of anchorage on seamounts (serving as pinning points) and increased warming. The U-shaped valley geometry has also influenced the glacier shrinkage processes and the redirection of glacial paleoflow during the last 300 years. The retreat rate to mid-20th century-2020 period is higher than Little Ice Age- mid-20th century period.
Abstract Active layer and permafrost are important indicators of climate changes in periglacial areas of Antarctica, and the soil thermal regime of Maritime Antarctica is sensitive to the current warming trend. This research aimed to characterize the active layer thermal regime of a patterned ground located at an upper marine terrace in Half Moon Island, during 2015-2018. Temperature and moisture sensors were installed at different soil depths, combined with air temperature, collecting hourly data. Statistical analysis was applied to describe the soil thermal regime and estimate active layer thickness. The thermal regime of the studied soil was typical of periglacial environment, with high variability in temperature and water content in the summer, resulting in frequent freeze-thaw cycles. We detected dominant freezing conditions, whereas soil temperatures increased, and the period of high soil moisture content lasted longer over the years. Active layer thickness varied between the years, reaching a maximum depth in 2018. Permafrost degradation affects soil drainage and triggers erosion in the upper marine terrace, where permafrost occurrence is unlikely. Longer monitoring periods are necessary for a detailed understanding on how current climatic and geomorphic conditions affect the unstable permafrost of low-lying areas of Antarctica (marine terraces).
Warming has been and is being enhanced at high latitudes or high elevations, whereas the quantitative estimation for warming from altitude and latitude effects has not been systematically investigated over Antarctic Ice Sheet, which covers more than 27 degrees of latitude and 4000 m altitude ranges. Based on the monthly surface air temperature data (1958–2020) from ERA5 reanalysis, this work aims to explore whether elevation-dependent warming (EDW) and latitude-dependent warming (LDW) exist. Results show that both EDW and LDW have the cooperative effect on Antarctic warming, and the magnitude of EDW is stronger than LDW. The negative EDW appears between 250 m and 2500 m except winter, and is strongest in autumn. The negative LDW occurs between 83 °S and 90 °S except in summer. Moreover, the surface downward long-wave radiation that related to the specific humidity, total cloud cover and cloud base height is a major contributor to the EDW over Antarctica. Further research on EDW and LDW should be anticipated to explore the future Antarctic amplification under different emission scenarios.
During the second half of the 20th century, the Antarctic Peninsula region has undergone a long and sustained warming period, followed by a shorter but also sustained cooling period, and then a very recent return to warming conditions. All of these have profoundly impacted the glaciers peripheral to the Antarctic Peninsula. This paper focuses on the analysis of the surface mass balance monitoring of such glaciers by the glaciological method, complemented by the analysis of mass-balance estimates by geodetic methods, as well as frontal ablation estimates. We aim to summarize the current knowledge and outline the main challenges faced by investigating the mass balance of such peripheral glaciers and their current contribution to sea-level rise. Motivation and current knowledge
Fildes Peninsula, on King George Island, has been greatly influenced by recent rapid climate warming. Lakes are pervasive features of Fildes Peninsula landscapes, some of which are used as water sources for Antarctic stations. We studied seven Fildes Peninsula lakes to explore differences among lakes and between seasons in phytoplankton and bacterioplankton communities. We measured environmental variables, analysed pigments using high-performance liquid chromatography and examined bacterial DNA through high-throughput sequencing of the 16S rRNA gene. The main driver structuring microbial communities was the season (i.e. spring vs autumn). Chlorophyceae were the dominant phytoplankton group in all lakes and both seasons. Indicator bacteria for each season were identified, including Flavobacterium , Polaromonas and Oxalobacteraceae as indicators of spring conditions under thick ice, whereas Frankiales and Verrucomicrobia were indicator species of autumn following the ice-free summer. The indicator species for spring are generally observed in oligotrophic conditions, whereas many of the autumn indicators are commonly found in soils. There were lesser between-lake differences in microbial communities in autumn, at the end of the open-water period, than in spring at the end of the ice-covered period. This study will act as the basis for future assessments of changes in aquatic microbial communities.
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Artykuł omawia zmiany warunków hydro-klimatycznych w rejonie Szetlandów Południowych i NW części Półwyspu Antarktycznego w latach 1979-2016. Są one istotne dla oceny zmian zachodzących w ekosystemach morskich i nadmorskich. Ogólną ich cechą jest przejście od fazy silnego ocieplenia do fazy ochładzania, co nastąpiło około 2000 r. Przedstawiono zmiany rocznej i sezonowej temperatury powietrza, temperatury powierzchni morza (SST) oraz powierzchni lodów morskich na morzach Bellingshausena i Weddella. Najsilniejszy spadek temperatury powietrza zaznacza się w okresie antarktycznego lata, na wszystkich stacjach zaznacza się spadek temperatury rocznej. Spadek SST następuje we wszystkich miesiącach roku, jest on wysoce istotny. Najsilniejszy spadek SST następuje również latem. Roczna powierzchnia zlodzona na Morzu Weddella systematycznie rośnie, zaznacza się szczególnie szybki przyrost powierzchni lodów w okresie luty-marzec. Roczna powierzchnia lodów na Morzu Bellingshausena po 2000 r. przestała spadać i zaznacza się w jej przebiegu słaby trend dodatni.
The timing and impact of deglaciation and Holocene readvances on the terrestrial continental margins of the Antarctic Peninsula (AP) have been well-studied but are still debated. Potter Peninsula on King George Island (KGI) (Isla 25 de Mayo), South Shetland Islands (SSI), NW Antarctic Peninsula, has a detailed assemblage of glacial landforms and stratigraphic exposures for constraining deglacial landscape development and glacier readvances. We undertook new morphostratigraphic mapping of the deglaciated foreland of the Warszawa Icefield, an outlet of the Bellingshausen (Collins) Ice Cap on Potter Peninsula, using satellite imagery and new lithofacies recognition and interpretations, combined with new chronostratigraphic analysis of stratigraphic sections, lake sediments, and moraine deposits. Results show that the deglaciation on Potter Peninsula began before c. 8.2 ka. Around c. 7.0 ka, the Warszawa Icefield and the marine-facing Fourcade Glacier readvanced across Potter Peninsula and to the outer part of Potter Cove. Evidence of further readvances on Potter Peninsula was absent until the Warszawa Icefield margin was landward of its present position on three occasions: c. 1.7–1.4 ka, after c. 0.7 ka (most likely c. 0.5–0.1 ka), and by 1956 CE. The timing of Holocene deglaciation and glacier fluctuations on Potter Peninsula are broadly coeval with other glacier- and ice-free areas on the SSI and the northern AP and likely driven by interactions between millennial–centennial-scale changes in solar insolation and irradiance, the southern westerlies, and the Southern Annular Mode.
The timing and impact of deglaciation and Holocene readvances on many ice-free terrestrial continental margins of the Antarctic Peninsula have been long-studied but remain debated. Potter Peninsula on King George Island (Isla 25 de Mayo), South Shetland Islands (SSI), NW Antarctic Peninsula has a detailed assemblage of glacial landforms, geomorphological features and stratigraphic exposures for constraining deglacial landscape development and glacier readvances. Here, we present a new geomorphological map of the deglaciated foreland of the Warszawa Icefield, an outlet of the Bellingshausen (Collins) Ice Cap on Potter Peninsula based on a combination of satellite imagery and new field investigations. Results from mapping and new lithofacies analysis and chronostratigraphic data from stratigraphic sections, lake sediments and moraine deposits show that deglaciation on Potter Peninsula began before c. 8.2 ka. Around c. 7.0 ka, the Warszawa Icefield and the marine terminating Fourcade Glacier readvanced across Potter Peninsula and to the outer areas of Potter Cove. Evidence of further readvances on Potter Peninsula is then absent until Warszawa Icefield front was landward of its present position on three occasions, c. 1.7–1.4 ka, after c. 0.7 ka (most likely c. 0.5–0.1 ka), and 1956 CE. Holocene deglaciation and glacier fluctuations on Potter Peninsula are broadly coeval with other ice-free areas on the South Shetland Islands and the northern Antarctic Peninsula, and likely driven by interactions between millennial-centennial scale changes in solar insolation and irradiance, the southern westerlies, and the Southern Annular Mode.
The large natural variability of the Antarctic sea ice is a key
characteristic of the system that might be responsible for the small
positive trend in sea ice extent observed since 1979. In order to gain
insight of the processes responsible for this variability, we have analysed
in a control simulation performed with a coupled climate model a positive
ice–ocean feedback that amplifies sea ice variations. When sea ice
concentration increases in a region, in particular close to the ice edge,
the mixed layer depth tends to decrease. This can be caused by a net inflow
of ice, and thus of freshwater, that stabilizes the water column. A second
stabilizing mechanism at interannual timescales is associated with the
downward salt transport due to the seasonal cycle of ice formation: brine is
released in winter and mixed over a deep layer while the freshwater flux
caused by ice melting is included in a shallow layer, resulting in a net
vertical transport of salt. Because of this stronger stratification due to
the presence of sea ice, more heat is stored at depth in the ocean and the
vertical oceanic heat flux is reduced, which contributes to maintaining a
higher ice extent. This positive feedback is not associated with a
particular spatial pattern. Consequently, the spatial distribution of the
trend in ice concentration is largely imposed by the wind changes that can
provide the initial perturbation. A positive freshwater flux could
alternatively be the initial trigger but the amplitude of the final response
of the sea ice extent is finally set up by the amplification related to
the ice–ocean feedback. Initial conditions also have an influence as the chance
to have a large increase in ice extent is higher if starting from a state
characterized by a low value.
Mesoscale model simulations are presented of a westerly föhn event over the
Antarctic Peninsula mountain ridge and onto the Larsen C ice shelf, just
south of the recently collapsed Larsen B ice shelf. Aircraft observations
showed the presence of föhn jets descending near the ice shelf surface
with maximum wind speeds at 250–350 m in height. Surface flux measurements
suggested that melting was occurring. Simulated profiles of wind speed,
temperature and wind direction were very similar to the observations.
However, the good match only occurred at a model time corresponding to
~9 h before the aircraft observations were made since the model
föhn jets died down after this. This was despite the fact that the model
was nudged towards analysis for heights greater than ~1.15 km above the
surface.
Timing issues aside, the otherwise good comparison between the model and
observations gave confidence that the model flow structure was similar to
that in reality. Details of the model jet structure are explored and
discussed and are found to have ramifications for the placement of automatic weather station
(AWS) stations on the ice shelf in order to detect föhn flow. Cross sections of
the flow are also examined and were found to compare well to the aircraft
measurements. Gravity wave breaking above the mountain crest likely created
a~situation similar to hydraulic flow and allowed föhn flow and ice shelf
surface warming to occur despite strong upwind blocking, which in previous
studies of this region has generally not been considered. Our results
therefore suggest that reduced upwind blocking, due to wind speed increases
or stability decreases, might not result in an increased likelihood of föhn
events over the Antarctic Peninsula, as previously suggested.
The surface energy budget of the model during the melting periods showed that
the net downwelling short-wave surface flux was the largest contributor to the
melting energy, indicating that the cloud clearing effect of föhn events is
likely to be the most important factor for increased melting relative to
non-föhn days. The results also indicate that the warmth of the föhn jets
through sensible heat flux ("SH") may not be critical in causing melting beyond
boundary layer stabilisation effects (which may help to prevent cloud cover
and suppress loss of heat by convection) and are actually cancelled by latent
heat flux ("LH") effects (snow ablation). It was found that ground heat flux ("GRD") was
likely to be an important factor when considering the changing surface energy
budget for the southern regions of the ice shelf as the climate warms.
We analyzed hydrographic data from the northwestern Weddell Sea continental shelf of the three austral winters 1989, 1997, and 2006 and two summers following the last winter cruise. During summer a thermal front exists at ~64° S separating cold southern waters from warm northern waters that have similar characteristics as the deep waters of the central basin of the Bransfield Strait. In winter, the whole continental shelf exhibits southern characteristics with high Neon (Ne) concentrations, indicating a significant input of glacial melt water. The comparison of the winter data from the shallow shelf off the tip of the Antarctic Peninsula, spanning a period of 17 yr, shows a salinity decrease of 0.09 for the whole water column, which has a residence time of <1 yr. We interpret this freshening as being caused by a combination of reduced salt input due to a southward sea ice retreat and higher precipitation during the late 20th century on the western Weddell Sea continental shelf. However, less salinification might also result from a delicate interplay between enhanced salt input due to sea ice formation in coastal areas formerly occupied by Larsen A and B ice shelves and increased Larsen C ice loss.
Since the 1950s, research stations on the Antarctic Peninsula have recorded some of the largest increases in near-surface air temperature in the Southern Hemisphere. This warming has contributed to the regional retreat of glaciers, disintegration of floating ice shelves and a 'greening' through the expansion in range of various flora. Several interlinked processes have been suggested as contributing to the warming, including stratospheric ozone depletion, local sea-ice loss, an increase in westerly winds, and changes in the strength and location of low-high-latitude atmospheric teleconnections. Here we use a stacked temperature record to show an absence of regional warming since the late 1990s. The annual mean temperature has decreased at a statistically significant rate, with the most rapid cooling during the Austral summer. Temperatures have decreased as a consequence of a greater frequency of cold, east-to-southeasterly winds, resulting from more cyclonic conditions in the northern Weddell Sea associated with a strengthening mid-latitude jet. These circulation changes have also increased the advection of sea ice towards the east coast of the peninsula, amplifying their effects. Our findings cover only 1% of the Antarctic continent and emphasize that decadal temperature changes in this region are not primarily associated with the drivers of global temperature change but, rather, reflect the extreme natural internal variability of the regional atmospheric circulation. © 2016 Macmillan Publishers Limited, part of Springer Nature. All rights reserved.
The heat is on
Rising surface air temperatures are understood to cause glacial melting, but it is becoming increasingly clear that the ocean also has a strong impact. Cook et al. studied glaciers that drain the Antarctic Peninsula and found a strong correlation between mid-depth ocean temperatures and glacier-front changes along the peninsula's western coastline. Glaciers in the south, which are exposed to warmer waters, have undergone significant retreat, while those in the northwest, which terminate in cooler waters, have not retreated as much or as uniformly. Thus, ocean-induced melting appears to be the main cause of glacial retreat in the region.
Science , this issue p. 283
The origins of the delayed increases in global surface temperature accompanying El Niño events and the implications for the role of diabatic processes in El Niño-Southern Oscillation (ENSO) are explored. The evolution of global mean surface temperatures, zonal means and fields of sea surface temperatures, land surface temperatures, precipitation, outgoing longwave radiation, vertically integrated diabatic heating and divergence of atmospheric energy transports, and ocean heat content in the Pacific is documented using correlation and regression analysis. For 1950-1998, ENSO linearly accounts for 0.06°C of global surface temperature increase. Warming events peak 3 months after SSTs in the Niño 3.4 region, somewhat less than is found in previous studies. Warming at the surface progressively extends to about ±30° latitude with lags of several months. While the development of ocean heat content anomalies resembles that of the delayed oscillator paradigm, the damping of anomalies through heat fluxes into the atmosphere introduces a substantial diabatic component to the discharge and recharge of the ocean heat content. However, most of the delayed warming outside of the tropical Pacific comes from persistent changes in atmospheric circulation forced from the tropical Pacific. A major part of the ocean heat loss to the atmosphere is through evaporation and thus is realized in the atmosphere as latent heating in precipitation, which drives teleconnections. Reduced precipitation and increased solar radiation in Australia, Southeast Asia, parts of Africa, and northern South America contribute to surface warming that peaks several months after the El Niño event. Teleconnections contribute to the extensive warming over Alaska and western Canada through a deeper Aleutian low and stronger southerly flow into these regions 0-12 months later. The 1976/1977 climate shift and the effects of two major volcanic eruptions in the past 2 decades are reflected in different evolution of ENSO events. At the surface, for 1979-1998 the warming in the central equatorial Pacific develops from the west and progresses eastward, while for 1950-1978 the anomalous warming begins along the coast of South America and spreads westward. The eastern Pacific south of the equator warms 4-8 months later for 1979-1998 but cools from 1950 to 1978.
Previous studies have shown strong contrasting trends in annual sea ice duration and in monthly sea ice concentration in two regions of the Southern Ocean: decreases in the western Antarctic Peninsula/southern Bellingshausen Sea (wAP/sBS) region and increases in the western Ross Sea (wRS) region. To better understand the evolution of these regional sea ice trends, we utilize the full temporal (quasi-daily) resolution of satellite-derived sea ice data to track spatially the annual ice edge advance and retreat from 1979 to 2004. These newly analyzed data reveal that sea ice is retreating 31 ± 10 days earlier and advancing 54 ± 9 days later in the wAP/sBS region (i.e., total change over 1979-2004), whereas in the wRS region, sea ice is retreating 29 ± 6 days later and advancing 31 ± 6 days earlier. Changes in the wAP/sBS and wRS regions, particularly as observed during sea ice advance, occurred in association with decadal changes in the mean state of the Southern Annular Mode (SAM; negative in the 1980s and positive in the 1990s) and the high-latitude response to El Niño-Southern Oscillation (ENSO). In general, the high-latitude ice-atmosphere response to ENSO was strongest when -SAM was coincident with El Niño and when +SAM was coincident with La Niña, particularly in the wAP/sBS region. In total, there were 7 of 11 -SAMs between 1980 and 1990 and the 7 of 10 +SAMs between 1991 and 2000 that were associated with consistent decadal sea ice changes in the wAP/sBS and wRS regions, respectively. Elsewhere, ENSO/SAMrelated sea ice changes were not as consistent over time (e.g., western Weddell, Amundsen, and eastern Ross Sea region), or variability in general was high (e.g., central/ eastern Weddell and along East Antarctica).
The Amundsen Sea sector of the West Antarctic ice sheet has been losing mass in recent decades; however, long records of snow accumulation are needed to place the recent changes in context. Here we present 300 year records of snow accumulation from two ice cores drilled in Ellsworth Land, West Antarctica. The records show a dramatic increase in snow accumulation during the twentieth century, linked to a deepening of the Amundsen Sea Low (ASL), tropical sea surface temperatures, and large-scale atmospheric circulation. The observed increase in snow accumulation and interannual variability during the late twentieth century is unprecedented in the context of the past 300 years and evidence that the recent deepening of the ASL is part of a longer trend.
The mass budget of the ice caps surrounding the Antarctica Peninsula and, in particular, the partitioning of its main components are poorly known. Here we approximate frontal ablation (i.e. the sum of mass losses by calving and submarine melt) and surface mass balance of the ice cap of Livingston Island, the second largest island in the South Shetland Islands archipelago, and analyse variations in surface velocity for the period 2007-2011. Velocities are obtained from feature tracking using 25 PALSAR-1 images, and used in conjunction with estimates of glacier ice thicknesses inferred from principles of glacier dynamics and ground-penetrating radar observations to estimate frontal ablation rates by a flux-gate approach. Glacier-wide surface mass-balance rates are approximated from in situ observations on two glaciers of the ice cap. Within the limitations of the large uncertainties mostly due to unknown ice thicknesses at the flux gates, we find that frontal ablation (-509 +/- 263 Mt yr(-1), equivalent to -0.73 +/- 0.38 m w.e. yr(-1) over the ice cap area of 697 km(2)) and surface ablation (- 0.73 +/- 0.10 m w.e. yr(-1)) contribute similar shares to total ablation (-1.46 +/- 0.39 m w. e. yr(-1)). Total mass change ( delta M = - 0.67 +/- 0.40 m w.e. yr(-1)) is negative despite a slightly positive surface mass balance (0.06 +/- 0.14 m w .e. yr(-1)). We find large interannual and, for some basins, pronounced seasonal variations in surface velocities at the flux gates, with higher velocities in summer than in winter. Associated variations in frontal ablation ( of similar to 237 Mt yr(-1); -0.34 m w.e. yr(-1)) highlight the importance of taking into account the seasonality in ice velocities when computing frontal ablation with a flux-gate approach.
Glaciers on the Antarctic Peninsula have recently shown changes in extent, velocity and thickness, yet there is little quantification of change in the mass balance of individual glaciers or the processes controlling changes in extent. Here a high-resolution digital elevation model and a semi-automated drainage basin delineation method have been used to define glacier systems between 63 degrees S-70 degrees S on the mainland and surrounding islands, resulting in an inventory of 1590 glacier basins. Of these, 860 are marine-terminating glaciers whose ice fronts can be defined at specific epochs since the 1940s. These ice front positions were digitized up to 2010 and the areas for all individual glacier basins were calculated. Glaciological characteristics, such as geometry, slope and altitudes, were attributed to each glacier, thus providing a new resource for glacier morphological analyses. Our results indicate that 90% of the 860 glaciers have reduced in area since the earliest recorded date. A north-south gradient of increasing ice loss is clear, as is distinct behaviour on the east and west coasts. The area lost varies considerably between glacier types, with correlations apparent with glacier shape, slope and frontal-type. Temporal trends indicate a uniform retreat since the 1970s, with a period of small re-advance in the late 1990s.
Mass balance researches on Bellingshausen Ice Dome (King George Island, archipelago Southern Shetland Islands, Antarctica) were spent during five summer seasons in 2007–1012 and one winter in 2011. The analysis of received data has shown that in 2007/08 and 2008/09 ice mass balance on Bellingshausen Ice Dome was almost closed to zero, in 2009/10, 2010/11 and 2011/12 it was positive. ELA in 2007/08 and 2008/09 was situated a little below top of the Ice Dome (about 225 m a.s.l.), in 2009/10 ELA has lowered practically up to sea level, in 2010/11 it was equal 180 m a.s.l., in 2011/12 – 220 m a.s.l. Good correlation between snow and ice melting and mean summer air temperature give possibility to renew ice melting conditions for all period of observations at Bellingshausen weather station (1969–2011). Ice mass balance for Bellingshausen Ice Dome was also renewed for similar period. Analysis of received data allow to suppose that tendency of climate cooling is outlined in last years.
We present new glacier mass-balance field data from Glaciar Bahía del Diablo, Vega Island, northeastern Antarctic Peninsula. The results provided here represent glacier mass-balance data over a 10 year period (2001-11) obtained by the glaciological and geodetic methods relying on field measurements. Glacier surface digital elevation models(DEMs) were obtained in 2001 and 2011 from a kinematic GPS field survey with high horizontal and vertical accuracies. In situ mass-balance data were collected from yearly stake measurements. The results attained by the two methods agree, which may be considered a measure of their accuracy. A cumulative mass change of -1.90 ± 0.31 m w.e. over the 10 year period was obtained from the annual mass-balance field surveys. The total mass change derived from DEM differencing was -2.16 ± 0.23 m w.e.
Growing evidence has demonstrated the importance of ice shelf buttressing on the inland grounded ice, especially if it is resting on bedrock below sea level. Much of the Southern Antarctic Peninsula satisfies this condition and also possesses a bed slope that deepens inland. Such ice sheet geometry is potentially unstable. We use satellite altimetry and gravity observations to show that a major portion of the region has, since 2009, destabilized. Ice mass loss of the marine-terminating glaciers has rapidly accelerated from close to balance in the 2000s to a sustained rate of -56 ± 8 gigatons per year, constituting a major fraction of Antarctica's contribution to rising sea level. The widespread, simultaneous nature of the acceleration, in the absence of a persistent atmospheric forcing, points to an oceanic driving mechanism.
Copyright © 2015, American Association for the Advancement of Science.
The climatic change on King George Island (KGI) in the South Shetland Islands, Antarctica, in the years of 1948–2011 are presented. In the reference period, a statistically significant increase in the air temperature (0.19°C/10 years, 1.2°C in the analysed period) occurred along with a decrease in atmospheric pressure (−0.36 hPa/10 years, 2.3 hPa). In winter time, the warming up is more than twice as large as in summer. This leads to decrease in the amplitude of the annual cycle of air temperature. On KGI, there is also a Warming trend of daily maximum and daily minimum air temperature. The evidently faster increase in daily minimum results in a decrease of the diurnal temperature range. The largest changes of air pressure took place in the summertime (−0.58 hPa/10 years) and winter (−0.34 hPa/10 years). The Semiannual Oscillation pattern of air pressure was disturbed. Climate changes on KGI are correlated with changing surface temperatures of the ocean and the concentration of sea ice. The precipitation on KGI is characterised by substantial variability year to year. In the analysed period, no statistically significant trend in atmospheric precipitation can be observed. The climate change on KGI results in substantial and rapid changes in the environment, which poses a great threat to the local ecosystem.
We present an update of the ‘key points’ from the Antarctic Climate Change and the Environment (ACCE) report that was published by the Scientific Committee on Antarctic Research (SCAR) in 2009. We summarise subsequent advances in knowledge concerning how the climates of the Antarctic and Southern Ocean have changed in the past, how they might change in the future, and examine the associated impacts on the marine and terrestrial biota. We also incorporate relevant material presented by SCAR to the Antarctic Treaty Consultative Meetings, and make use of emerging results that will form part of the Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report.
Editors note: For easy download the posted pdf of the State of the Climate for 2011 is a very low-resolution file. A high-resolution copy of the report is available by clicking here. Please be patient as it may take a few minutes for the high-resolution file to download. Supplemental figures and datasets are available here.
We examine the evolution of sea-ice extent (SIE) over both polar regions for 35 years from November 1978 to December 2013, as well as for the global total ice (Arctic plus Antarctic). Our examination confirms the ongoing loss of Arctic sea ice, and we find significant (p< 0.001) negative trends in all months, seasons and in the annual mean. The greatest rate of decrease occurs in September, and corresponds to a loss of 3 × 106km2 over 35 years. The Antarctic shows positive trends in all seasons and for the annual mean (p<0.01), with summer attaining a reduced significance (p<0.10). Based on our longer record (which includes the remarkable year 2013) the positive Antarctic ice trends can no longer be considered 'small', and the positive trend in the annual mean of (15.29 ± 3.85) × 103 km2 a-1 is almost one-third of the magnitude of the Arctic annual mean decrease. The global annual mean SIE series exhibits a trend of (-35.29±5.75) × 103km2a-1 (p<0.01). Finally we offer some thoughts as to why the SIE trends in the Coupled Model Intercomparison Phase 5 (CMIP5) simulations differ from the observed Antarctic increases.
This Supplementary Information contains:
1. Supplementary Discussion
1.1. Byrd 1980s warming and atmospheric circulation over the Ross-Amundsen Seas
2. Supplementary Methods
2.1. Background on the temperature observations from Byrd Station/AWS
2.1.1. Historical background
2.1.2. Corrections to Byrd AWS observations from 1989–01/2011
2.1.3. Potential sources of error in the AWS observations
2.2. Details on the infilling method
2.2.1. Infilling of the Byrd record: 1979–2011 period (alternative method)
2.2.2. ERA-Interim forecast versus analysis temperatures
2.3. Uncertainty calculation
2.3.1 Uncertainties of the reconstructed temperatures
2.3.2 Uncertainties of the temperature trends
3. Supplementary Material
3.1. Global reanalysis data
3.2. Global temperature data
4. References
5. Supplementary Figures
5.1. Figures related to the main text discussion
5.2. Figures related to the infilling method
6. Supplementary Tables
This Supplementary Information contains:
1. Revisions to Byrd temperatures from 1957-1975
1.1. Byrd temperature record in READER
1.2. Recalculation of the monthly mean temperatures
1.3. Sources of temperature observations
1.4. Remarks about specific months
1.5. References
1.6. Table and figures relevant to Section 1
2. Updated figures and tables from Bromwich et al. (2013)
The Randolph Glacier Inventory (RGI) is a globally complete collection of digital outlines of
glaciers, excluding the ice sheets, developed to meet the needs of the Fifth Assessment of the
Intergovernmental Panel on Climate Change for estimates of past and future mass balance. The RGI was
created with limited resources in a short period. Priority was given to completeness of coverage, but a
limited, uniform set of attributes is attached to each of the �198 000 glaciers in its latest version, 3.2.
Satellite imagery from 1999–2010 provided most of the outlines. Their total extent is estimated as
726 800�34 000km2. The uncertainty, about �5%, is derived from careful single-glacier and basin-scale
uncertainty estimates and comparisons with inventories that were not sources for the RGI. The main
contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover.
These errors appear not to be normally distributed, and quantifying them reliably is an unsolved problem.
Combined with digital elevation models, the RGI glacier outlines yield hypsometries that can be combined
with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers.
The RGI has already proved its value in the generation of significantly improved aggregate estimates of
glacier mass changes and total volume, and thus actual and potential contributions to sea-level rise.
Previously unknown foehn jets have been identified to the east of the Antarctic Peninsula ( AP ) above the Larsen C Ice Shelf. These jets have major implications for the east coast of the AP , a region of rapid climatic warming and where two large sections of ice shelf have collapsed in recent years.
During three foehn events across the AP , leeside warming and drying is seen in new aircraft observations and simulated well by the Met Office Unified Model ( MetUM ) at ∼1.5 km grid spacing. In case A, weak southwesterly flow and an elevated upwind inversion characterise a highly nonlinear flow regime with upwind flow blocking. In case C strong northwesterly winds characterise a relatively linear case with little upwind flow blocking. Case B resides somewhere between the two in flow regime linearity.
The foehn jets – apparent in aircraft observations where available and MetUM simulations of all three cases – are mesoscale features (up to 60 km in width) originating from the mouths of leeside inlets. Through back trajectory analysis they are identified as a type of gap flow. In cases A and B the jets are distinct, being strongly accelerated relative to the background flow, and confined to low levels above the Larsen C Ice Shelf. They resemble the ‘shallow foehn’ of the Alps. Case C resembles a case of ‘deep foehn’, with the jets less distinct. The foehn jets are considerably cooler and moister relative to adjacent regions of calmer foehn air. This is due to a dampened foehn effect in the jet regions: in case A the jets have lower upwind source regions, and in the more linear case C there is less diabatic warming and precipitation along jet trajectories due to the reduced orographic uplift across the mountain passes.
The Randolph Glacier Inventory (RGI) is a globally complete collection of digital outlines of glaciers, excluding the ice sheets, developed to meet the needs of the Fifth Assessment of the Intergovernmental Panel on Climate Change for estimates of past and future mass balance. The RGI was created with limited resources in a short period. Priority was given to completeness of coverage, but a limited, uniform set of attributes is attached to each of the ∼198 000 glaciers in its latest version, 3.2. Satellite imagery from 1999–2010 provided most of the outlines. Their total extent is estimated as 726 800±34 000 km2. The uncertainty, about ±5%, is derived from careful single-glacier and basin-scale uncertainty estimates and comparisons with inventories that were not sources for the RGI. The main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover. These errors appear not to be normally distributed, and quantifying them reliably is an unsolved problem. Combined with digital elevation models, the RGI glacier outlines yield hypsometries that can be combined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers. The RGI has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume, and thus actual and potential contributions to sea-level rise.
Changes in sea ice significantly modulate climate change because of its high reflective and strong insulating nature. In contrast to Arctic sea ice, sea ice surrounding Antarctica has expanded1, with record extent2 in 2010. This ice expansion has previously been attributed to dynamical atmospheric changes that induce atmospheric cooling3. Here we show that accelerated basal melting of Antarctic ice shelves is likely to have contributed significantly to sea-ice expansion. Specifically, we present observations indicating that melt water from Antarctica’s ice shelves accumulates in a cool and fresh surface layer that shields the surface ocean from the warmer deeper waters that are melting the ice shelves. Simulating these processes in a coupled climate model we find that cool and fresh surface water from ice-shelf melt indeed leads to expanding sea ice in austral autumn and winter. This powerful negative feedback counteracts Southern Hemispheric atmospheric warming. Although changes in atmospheric dynamics most likely govern regional sea-ice trends4, our analyses indicate that the overall sea-ice trend is dominated by increased ice-shelf melt. We suggest that cool sea surface temperatures around Antarctica could offset projected snowfall increases in Antarctica, with implications for estimates of future sea-level rise.
Topography exerts a key role in controlling permafrost distribution in areas where mean annual temperatures are slightly negative. One such case is the low-altitude environments of Maritime Antarctica, where permafrost is sporadic to discontinuous below 20–40 m asl and continuous at higher areas and active layer dynamics are thus strongly conditioned by geomorphological setting. In January 2014 we installed three sites for monitoring active layer temperatures across Byers Peninsula (Livingston Island, South Shetland Islands) at elevations between 45 and 100 m. The sites are situated in lake catchments (lakes Escondido, Cerro Negro, and Domo) that have different geomorphological and topographical conditions. Our objective was to examine the role of topography and microclimatic conditions in determining the active layer thermal regime in order to identify the factors that control geomorphic processes in these lake catchments. At each site a set of loggers was installed to monitor air temperature (AT), snow thickness (SwT) and soil temperature (ST) down to 80 cm depth. Mean annual air temperatures (MAAT) showed similar values in the three sites (− 2.7 to − 2.6 °C) whereas soil temperatures showed varying active layer thicknesses at the three catchments. The ground thermal regime was strongly controlled by soil properties and snow cover thickness and duration, which is influenced by local topography. Geomorphological processes operating at the lake catchment scale control lacustrine sedimentation processes, and both are dependent on the combination of topographical and climatic conditions. Therefore, the interpretation of lake sediment records from these three lakes requires that soil thermal regime and snow conditions at each site be taken into account in order to properly isolate the geomorphological, environmental and climatic signals preserved in these lake records.
Antarctic sea-ice extent has been slowly increasing in the satellite record that began in 1979. Since the late 1990s, the increase has accelerated, but the average of all climate models shows a decline. Meanwhile, the Interdecadal Pacific Oscillation, an internally generated mode of climate variability, transitioned from positive to negative, with an average cooling of tropical Pacific sea surface temperatures, a slowdown of the global warming trend and a deepening of the Amundsen Sea Low near Antarctica that has contributed to regional circulation changes in the Ross Sea region and expansion of sea ice. Here we show that the negative phase of the Interdecadal Pacific Oscillation in global coupled climate models is characterized by anomalies similar to the observed sea-level pressure and near-surface 850 hPa wind changes near Antarctica since 2000 that are conducive to expanding Antarctic sea-ice extent, particularly in the Ross Sea region in all seasons, involving a deepening of the Amundsen Sea Low. These atmospheric circulation changes are shown to be mainly driven by precipitation and convective heating anomalies related to the Interdecadal Pacific Oscillation in the equatorial eastern Pacific, with additional contributions from convective heating anomalies in the South Pacific convergence zone and tropical Atlantic regions.
This chapter deals with the Antarctic Peninsula (AP) exclusive of the South Shetland and South Orkney Islands, which will be considered in Chap. 13, and the Joinville and James Ross Island group along the east coast of the AP, which will be considered in Chap. 14. It is disconcerting that so few soil investigations have been conducted along the AP, especially in view of the rapid warming along the western Antarctic Peninsula (WAP), which is expanding the ice-free area. The WAP is unique from other areas in Antarctica, because of its relatively temperate climate and the strong influence that biology plays in soil-forming processes.
The floating ice shelves along the seaboard of the Antarctic ice sheet restrain the outflow of upstream grounded ice. Removal of these ice shelves, as shown by past ice-shelf recession and break-up, accelerates the outflow, which adds to sea-level rise. A key question in predicting future outflow is to quantify the extent of calving that might precondition other dynamic consequences and lead to loss of ice-shelf restraint. Here we delineate frontal areas that we label as passive shelf ice'and that can be removed without major dynamic implications, with contrasting results across the continent. The ice shelves in the Amundsen and Bellingshausen seas have limited or almost no passive'portion, which implies that further retreat of current ice-shelf fronts will yield important dynamic consequences. This region is particularly vulnerable as ice shelves have been thinning at high rates for two decades and as upstream grounded ice rests on a backward sloping bed, a precondition to marine ice-sheet instability. In contrast to these ice shelves, Larsen C Ice Shelf, in the Weddell Sea, exhibits a large passive'frontal area, suggesting that the imminent calving of a vast tabular iceberg will be unlikely to instantly produce much dynamic change.
Cartographic data and satellite images have revealed that the area of the Livingston ice cap decreased by 4.31% from 1956 to 1996. Local factors, mainly topographic, have an influence on advances and retreats of the ice front. We established a simple model which correlates the reduction of the ice cap and the atmospheric warming detected in the Antarctic Peninsula during the last few decades.
The simplicity of maritime Antarctic terrestrial ecosystems, combined with rapid changes in several environmental variables, creates a natural laboratory probably unparalleled worldwide in which to study biological consequences of climate change. The Antarctic Peninsula and Scotia Arc provide a gradient from oceanic cool temperate to frigid continental desert conditions, giving a natural model of climate change predictions. Biota are limited by the twin environmental factors of low temperature and lack of water, while also facing changes in the timing of UV-B maxima, associated with the spring ozone hole. Biological changes consistent with predictions from climate amelioration are visible in the form of expansions in range and local population numbers amongst elements of the flora. Field manipulations demonstrate (i) potential for massive species and community responses to climate amelioration, (ii) the importance of existing soil propagule banks, and (iii) biochemical responses to changing radiation environments. Antarctic species possess considerable resistance/resilience and response flexibility to a range of environmental stresses. Wide environmental variability in Antarctic terrestrial habitats also means that predicted levels of change often fall well within the range already experienced. Thus, climate amelioration may generate positive responses from resident biota, at least while they remain protected through isolation from colonization by more effective competitors. Responses are likely to be subtle and multifactorial in origin, arising from changes in resource allocation and energy economics. The integration of subtle responses may lead to greater consequential impacts in communities and ecosystems.
The response of active-layer thickness and the ground thermal regime to climatic conditions on the Ulu Peninsula (James Ross Island, northeastern Antarctic Peninsula) in 2011–13 is presented. The mean air temperature over this period was –8.0°C and ground temperature at 5 cm depth varied from –6.4°C (2011–12) to –6.7°C (2012–13). The active-layer thickness ranged between 58 cm (January 2012) and 52 cm (February 2013). Correlation analyses indicate that air temperature affects ground temperature more significantly on snow-free days (R2 = 0.82) than on snow cover days (R2 = 0.53). Although the effect of snow cover on the daily amplitude of ground temperature was observable to 20 cm depth, the overall influence of snow depth on ground temperature was negligible (freezing n-factor of 0.95–0.97). Copyright © 2015 John Wiley & Sons, Ltd.
The origin and nature of seal carcasses scattered around the Ulu Peninsula, James Ross Island, is examined using robust and novel multidisciplinary analysis. Spatial distribution analysis indicates their predominance at low elevations and on surfaces with negligible slope. The seals died throughout the last century. Dental cement increments indicate that the seals died in late winter, and we interpret this to show an influence of the persistence and break-up of sea ice and the appearance of pools/cracks in the northern Prince Gustav Channel on death. Specifically, after being trapped by a late winter freeze-up the seals search for open water, become disoriented by snow-covered flat valleys and move inland. Carcasses from all age groups of crabeater seal are found on land, but inland movement is less notable for Weddell and leopard seals. Although most carcasses appear to have remained unchanged during the last 10 years due to the cold and dry conditions, a few carcasses that are located in sites of snow accumulation and subsequent melting have undergone enhanced decay. Decaying seal carcasses represent loci of nutrient release in a nutrient deficient environment and are colonized by algae, cyanobacteria, lichens and mosses. This research suggests further useful studies for the future.
The scientific literature portrays a temporally invariant spatial relationship between the phase of the southern annular mode (SAM) and the sign of surface air temperature (SAT) anomalies across Antarctica. However, here the authors describe a predominant switch from a negative to positive SAM-temperature relationship (STR) across East Antarctica in austral summer/autumn during the first decade of the twenty-first century, when the SAM was generally weakly positive. Of the nine years that had a positive regional STR from 1957 to 2010, seven occurred during the last decade. This reversal appears to be a response to anomalous high pressure over East Antarctica, resulting from variability in the phase and amplitude of the local component of the zonal wavenumber 3 pressure pattern. In years when a reversed (positive) regional STR exists the anomalous circulation is such that there is greater energy flux into the region, while enhanced katabatic drainage across the continental interior disrupts the surface temperature inversion leading to warmer SATs inland, too. The average summer/autumn SAT increase across East Antarctica for years with reversed versus standard STR is similar to 1 degrees C. Anthropogenically forced models fail to reproduce the trend toward the anomalous high pressure pattern so it is likely that the STR switch is due to natural internal climate variability. That such broadscale STR reversals can take place on decadal time scales needs to be considered when detecting and attributing recent Antarctic climate change and when utilizing isotope data from the East Antarctic ice core record to provide a proxy SAM index prior to the instrumental record.
Topography exerts a key role on permafrost distribution in areas where mean annual temperatures are slightly negative. This is the case of low-altitude environments in Maritime Antarctica, namely in the South Shetland Islands, where permafrost is marginal to discontinuous until elevations of 20-40 m asl turning to continuous at higher areas. Consequently, the active layer dynamics is also strongly conditioned by the geomorphological setting. In January 2014 we installed three sites for monitoring the active layer dynamics across the Byers Peninsula (Livingston Island, South Shetland Islands) in different geomorphological environments at elevations between 60 and 100 m. The purpose was to examine the role of the topography and microclimatic conditions on the active layer dynamics. At each site a set of loggers was set up to monitor: air temperatures, snow thickness, ground temperatures until 80 cm together with the coupling atmosphere-ground temperatures. During the first year of monitoring the mean annual air temperatures show similar values in the three sites, in all cases slightly below freezing. The snowy conditions during this year in this archipelago have resulted in a late melting of snow, which has also conditioned the duration of frozen conditions in the uppermost soil layers. Topography has a strong influence on snow cover duration, which in turn affects frozen ground conditions. The Domo site is located in a higher position with respect to the central plateau of Byers; here, the wind is stronger and snow cover thinner, which has conditioned a longer thawing season than in the other two sites (Cerro Negro, Escondido). These two sites are located in topographically protected areas favouring snow accumulation. The longer persistence of snow conditions a longer duration of negative temperatures in the active layer of the permafrost.
The recently deglaciated environments in maritime permafrost regions are usually affected by very active paraglacial processes. Elephant Point is an ice-free area of 1.16 km2 located in the SW of Livingston island (South Shetland Islands, Antarctica). Between 1956-2010 the retreat of the ice cap covering most part of this island has exposed 17.3% of the land surface in this peninsula. Two geomorphological units were identified in this new ice-free area: a moraine extending from the western to the eastern coastlines and a relatively flat proglacial surface. The glacier in 1956 sat in contact with the northern slope of the moraine, but its accelerated retreat-in parallel to the warming trend recorded in the Antarctic Peninsula-left these areas free of glacier ice. Subsequently, the postglacial evolution was controlled by the relaxation phase typical of paraglacial systems. The typology and intensity of geomorphological processes show a significantly different dynamics between the southern and northern slopes of the moraine. This pattern is related to the different stage of paraglacial adjustment in both slopes. In the southern side, on coarser sediments, pronival ramparts, debris flows and alluvial fans are distributed, with a low to moderate activity of slope processes. In the northern side, mass wasting processes are extremely active on fine-grained unconsolidated sediments. Ice-rich permafrost is being degraded by thermokarst processes. Landslides and mudflows transfer large amounts of sediments down-slope. The surface affected by retrogressive-thaw slumps in the moraine has been quantified in 24,172 m2, which accounts for 9.6% of its surface. The abundance of kettle-lakes is also indicative of the degradation of the ground ice. Paraglacial processes are expected to continue in the moraine and proglacial area in the near future, although their intensity and duration will depend on the magnitude and rate of future climate trends in the northern Antarctic Peninsula.
The occurrence of coreless winters in the South Shetland Islands region is re− lated to increase in the intensity of cyclonic circulation and to the presence of massive and rapid advection of warm air northerly and westerly. Coreless winter developments depend on large−scale oceanic processes – the presence of positive anomalies in sea surface temper− ature (SST) in the Bellingshausen Sea over the range 080°–092°W and the retreat of sea ice extent southwards. When negative anomalies of SST in the same region are observed and the sea ice extent advances northwards, a winter with clearly marked cold core is experi− enced at the Arctowski Station on the South Shetlands.