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1. The area of study in the Chilean Andes, about 33 AE S 70 AE W. Vertical grid separation is about 111 km (1 AE latitude). Map source: South America map from the GLOBE project, NOAA, NGDC,
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Water as a result of snow and glacier melt is an important resource in the Central Andes of Chile and Argentina, which in terms of precipitation are close to climatic deserts, yet they support large populations and a rich agriculture. In spite of this, little is known of the processes at play and the variability over time. In particular, the specif...
Citations
... In northern SA, small zenith angles and a thin, dry, and cloud-free atmosphere during most of the year MacDonell et al., 2013b) make incoming short-wave radiation and high air temperatures the most important sources of seasonal variations in the energy available for melt (e.g., Ayala et al., 2017aAyala et al., , 2017bCorripio, 2003). Melt dominates ablation at lower elevation sites, but as elevation increases, so does the importance of sublimation (Ayala et al., 2017b). ...
... One peculiarity of glacier surfaces in the SA is the formation of snow or ice spikes, or penitentes ( Figure 3), due to the high rates of sublimation combined with intense solar radiation levels (Corripio, 2003). Penitentes are an ablation morphology that improves the conservation of snow cover, depending on its opening angle, shape and spatial variability of the albedo (Corripio 2003;Corripio and Purves, 2005;Lhermitte et al., 2014). ...
... One peculiarity of glacier surfaces in the SA is the formation of snow or ice spikes, or penitentes ( Figure 3), due to the high rates of sublimation combined with intense solar radiation levels (Corripio, 2003). Penitentes are an ablation morphology that improves the conservation of snow cover, depending on its opening angle, shape and spatial variability of the albedo (Corripio 2003;Corripio and Purves, 2005;Lhermitte et al., 2014). Their existence causes non-linear ablation (Nicholson et al., 2016) due to the prevalence of sublimation at the top of the cones and melt at the bottom (Corripio and Purves, 2005;Sinclair and MacDonell, 2016). ...
Semiarid Andean headwaters are key components of the hydrological system of north-central Chile as this is the main source of runoff which supports ecosystems and population located downstream. This study develops a conceptual hydrological model of the Chilean semiarid Andes headwaters, based on an integrative critical analysis of the current state of published research in the region. We combine a plethora of literature focused on isolated hydrological units including extensive literature on glacier and snowpack hydrological processes and less abundant literature on permafrost landforms, groundwater dynamics and other hydrological features. Among others, we identify important knowledge gaps related to the hydrogeomorphological understanding of permafrost area and its interaction with groundwater, as well as deep aquifer recharge and circulation. These two research topics are necessary next steps to better constrain model predictions of catchment response to future climatic scenarios associated with decreasing water contribution from glaciers and precipitation.
... Although this implies that the model is not strictly mass-conserving, we verify that the discarded snow is, on average, 34 mm yr -1 over the entire basin (or 688 mm yr -1 = 1.9 mm d -1 over the areas above 5000 m a.s.l.), which is similar to the estimates of sublimation amounts for this region (Corripio, 2003;Ayala et al., 2017a, b) and is on the order of the model uncertainties (49.9 mm w.e. in Figure 6.4-2a). As elevation decreases south, the discarded snow varies from about 121 mm w.e. ...
Glaciers on Earth along other components of the cryosphere are important for the climate system. However, it is widely known that the vast majority of glaciers are retreating and thinning since the early part of the 20th century. Additionally, future projections have highlighted that at the end of the 21st century, glaciers are going to lose a considerable part of their remaining mass. These glacier changes have several implications for physical, biological and human systems, affecting the water availability for downstream communities and contribute to sea level rise. Unlike other regions, where glaciers are less relevant for the overall hydrology, glaciers in South America constitute a critical resource since minimum flow levels in headwaters of the Andean mountains are usually sustained by ice melt, especially during late summer and droughts, when the contribution from the seasonal snow cover is depleted. In the last decades, the number of studies has increased considerable, however, in the Southern Andes and the surrounding sub-Antarctic islands glaciers still are less studied in comparison with their counterparts in the Northern Hemisphere. The few studies on glacier mass balance in this region suggest a risk of water scarcity for many Andean cities which freshwater supply depends on glacial meltwater. Additionally, glaciers on sub-Antarctic islands have not been completely assessed and their contribution to the sea level rise has been roughly estimated. Hence, the monitoring of glaciers is critical to provide baseline information for regional climate change adaptation policies and facilitate potential hazard assessments. Close and long-range remote sensing techniques offer the potential for repeated measurements of glacier variables (e.g. glacier mass balance, area changes). In the last decades, the number of sensors and methods has increased considerably, allowing time series analysis as well as new and more precise measurements of glacier changes. The main goal of this thesis is to investigate and provide a detailed quantification of glacier elevation and mass changes of the Southern Andes with strong focus on the Central Andes of Chile and South Georgia. Six comprehensive studies were performed to provide a better understanding of the development and current status of glaciers in this region. Overall, the glacier changes were estimated by means of various remote sensing techniques. For the Andes as a whole, the first continent-wide glacier elevation and mass balance was conducted for 85% of the total glacierized area of South America. A detailed estimation of mass changes using the bi-static synthetic aperture radar interferometry (Shuttle Radar Topography Mission -SRTM- and TerraSAR-X add-on for Digital Elevation Measurements -TanDEM-X- DEMs) over the years 2000 to 2011/2015 was computed. A total mass loss rate of 19.43 ± 0.60 Gt a-1 (0.054 ± 0.002 mm a-1 sea level rise contribution) from elevation changes above ground, sea or lake level was calculated, with an extra 3.06 ± 1.24 Gt a-1 derived from subaqueous ice mass loss. The results indicated that about 83% of the total mass loss observed in this study was contributed by the Patagonian icefields (Northern and Southern), which can largely be explained by the dynamic adjustments of large glaciers. For the Central Andes of Chile, four studies were conducted where detailed times series of glacier area, mass and runoff changes were performed on individual glaciers and at a region level (Maipo River basin). Glaciers in the central Andes of Chile are a fundamental natural resources since they provide freshwater for ecosystems and for the densely populated Metropolitan Region of Chile. The first study was conducted in the Maipo River basin to obtain time series of basin-wide glacier mass balance estimates. The estimations were obtained using historical topographic maps, SRTM, TanDEM-X, and airborne Light Detection and Ranging (LiDAR) digital elevation models. The results showed spatially heterogeneous glacier elevation and mass changes between 1955 and 2000, with more negative values between 2000 and 2013. A mean basin-wide glacier mass balance of −0.12 ± 0.06 m w.e. a-1 , with a total mass loss of 2.43 ± 0.26 Gt between 1955–2013 was calculated. For this region, a 20% reduction in glacier ice volume since 1955 was observed with associated consequences for the meltwater contribution to the local river system. Individual glacier studies were performed for the Echaurren Norte and El Morado glaciers. Echaurren Norte Glacier is a reference glacier for the World Glacier Monitoring Service. An ensemble of different data sets was used to derive a complete time series of elevation, mass and area changes. For El Morado Glacier, a continuous thinning and retreat since the 20th century was found. Overall, highly negative elevation and mass changes rates were observed from 2010 onwards. This coincides with the severe drought in Chile in this period. Moreover, the evolution of a proglacial lake was traced. If drained, the water volume poses an important risk to down-valley infrastructure. The glacier mass balance for the Central Andes of Chile has been observed to be highly correlated with precipitation (ENSO). All these changes have provoked a glacier volume reduction of one-fifth between 1955 and 2016 and decrease in the glacier runoff contribution in the Maipo basin. The thesis closes with the first island-wide glacier elevation and mass change study for South Georgia glaciers, one of the largest sub-Antarctic islands. There, glaciers changes were inferred by bi-static synthetic aperture radar interferometry between 2000 and 2013. Frontal area changes were mapped between 2003 and 2016 to roughly estimate the subaqueous mass loss. Special focus was given to Szielasko Glacier where repeated GNSS measurements were available from 2012 and 2017. The results showed an average glacier mass balance of −1.04 ± 0.09 m w.e. a-1 and a mass loss rate of 2.28 ± 0.19 Gt a-1 (equivalent to 0.006 ± 0.001 mm a-1 sea level rise) in the period 2000-2013. An extra 0.77 ± 0.04 Gt a-1 was estimated for subaqueous mass loss. The concurrent area change rate of the marine and lake-terminating glaciers amounts to −6.58 ± 0.33 km2 a-1 (2003–2016). Overall, the highest thinning and retreat rates were observed for the large outlet glaciers located at the north-east coast. Neumayer Glacier showed the highest thinning rates with the disintegration of some tributaries. Our comparison between InSAR data and GNSS measurements showed good agreement, demonstrating consistency in the glacier elevation change rates from two different methods. Our glacier elevation and mass changes assessment provides a baseline for further comparison and calibration of model projection in a sparsely investigated region. Future field measurements, long-term climate reanalysis, and glacier system modelling including ice-dynamic changes are required to understand and identify the key forcing factors of the glacier retreat and thinning.
... The surface roughness length z 0 can be interpreted as the height at which the wind speed is zero (ranging from 0.001 mm to a few centimeters) (Corripio, 2003). From fresh snow to aged snow, z 0 increases linearly from 0.24 mm to 4 mm (Gromke et al., 2011), for the ice surface, we assumed z 0 =1.7 mm, by following Cullen et al. (2007). ...
Glaciers, as massive freshwater reservoirs, support the planet's living systems and have an impact on our daily lives, even for communities living far away. Ongoing and future climate change is predicted to have strong impacts on the mass balance of alpine glacier around the world. To understand the relationship between climate and glacier dynamics, a range of mass balance models are currently used. Most of these models however, ignore subsurface heat fluxes as a component of glacier mass balance. Here, we set out to investigate the importance of subsurface heat flux for the mass balance of an alpine glacier using a surface energy mass balance model (SEM) coupled with a multilayer subsurface heat conduction model (MSHCM) that resolves the subsurface glacier temperature. As a case study, we investigate the Urumqi Glacier No.1 in the Tianshan Mountains (NW China), which has a long and continuous time series of surface and subsurface glacier temperature measurements. We evaluate the results of both glacier temperature models (SEM and MSHCM) using these in situ observations and investigate the sensitivity of mass balance to five meteorological factors: air temperature, precipitation, incoming shortwave radiation, relative humidity, and wind speed. The mass balance of the glacier was simulated first by including the influence of subsurface heat flux, and second, the subsurface heat flux was neglected. Observed and simulated mass balance and the englacial temperature were found to be reasonably close in both cases. Furthermore, the mass balance was simulated with a zero surface temperature assumption, which resulted in a 6% overestimation of the summer ablation. We concluded that the mass balance of Urumqi Glacier No.1 was most sensitive to variations in temperature, followed by precipitation. Furthermore, our results show that subsurface heat flux in the ablation area can generally be neglected in estimating the mass balance of alpine glaciers during ablation season.
... Interpolated fields from the point measurements arein the case of temperature, precipitation, humidity, and wind speedobtained using a combined lapse rate-inverse distance weighting scheme, either using automatically calculated lapse rates for each time step or using prescribed monthly lapse rates. Radiation fluxes are calculated for clear-sky conditions using the parameterizations from Corripio (2002) and corrected using cloudiness fields (Hanzer et al., 2016). Similar approaches were applied for the SNOWPACK/Alpine3D simulations by using the meteorological preprocessing library MeteoIO (Bavay and Egger, 2014). ...
Snow management, i. e., snowmaking and grooming, is an integral part of modern ski resort management. While the current snow cover distribution on the slopes is often well known thanks to the usage of advanced monitoring techniques, information about its future evolution is usually lacking. Management-enabled numerical snowpack models driven by meteorological forecasts can help to fill this gap.
In the frame of the H2020 project PROSNOW, the snowpack models AMUNDSEN, Crocus, and SNOWPACK/Alpine3D are applied in nine pilot ski resorts across the European Alps for forecasting snow conditions in time scales from days to several months ahead. We present the integration of detailed snowmaking and grooming practices implemented in the three models and show how they can be adapted to individual ski resorts. An ensemble of snow management configurations accounting for a comprehensive set of possible tactical and strategic operational choices is introduced, along with an approach to homogeneously spatialize the results of the three snow models over different areas of the ski resorts. First simulation results are presented for the nine pilot ski resorts in the form of distributed snow water equivalent (SWE) maps along with SWE and snow depth time series for two selected seasons in the past.
... Those parameters were not included in their model for Europa. On the other hand, the 2:1 ratio used by Hobley et al. 1 is from measurements of Chilean penitentes 11 and experiments simulating Earth 4 . The reader is thus left with conflicting interpretations of the atmospheric regime on which Hobley et al. 1 is based: their sublimation depth calculations depend on kinetic theory for a hard vacuum, but the 2:1 spacing is dependent on Earth conditions. ...
... As snow on this high-elevation areas is in reality removed by wind transport and sublimation, we reset the SWE in the model to zero at the beginning of each hydrological year. Although 285 this implies that the model is not strictly mass-conserving, we verify that the discarded snow is in average 34 mm yr -1 over the entire basin (or 688 mm yr -1 = 1.9 mm d -1 over the areas above 5000 m a.s.l.), which is a reasonable estimate of sublimation amounts for this region (Corripio, 2003;Ayala et al., 2017b), and is in the order of the model uncertainties (see Figure 2). Table 1, whereas values for the sub-surface flux parameters are shown in the supplementary information (Table S1). ...
Abstract. As glaciers adjust their size in response to climate variations, long-term changes in meltwater production can be expected, affecting the local availability of water resources. We investigate glacier runoff in the period 1955–2016 in the Maipo River Basin (4 843 km<sup>2</sup>), semiarid Andes of Chile. The basin contains more than 800 glaciers covering 378 km<sup>2</sup> (inventoried in 2000). We model the mass balance and runoff contribution of 26 glaciers with the physically-oriented and fully-distributed TOPKAPI-ETH glacio-hydrological model, and extrapolate the results to the entire basin. TOPKAPI-ETH is run using several glaciological and meteorological datasets, and its results are evaluated against streamflow records, remotely-sensed snow cover and geodetic mass balances for the periods 1955–2000 and 2000–2013. Results show that glacier mass balance had a general decreasing trend as a basin average, but with differences between the main sub-catchments. Glacier volume decreased by one fifth (from 18.6 ± 4.5 to 14.9 ± 2.9 km<sup>3</sup>). Runoff from the initially glacierized areas was 186 ± 27 mm yr<sup>−1</sup> (17 ± 7 % of the total contributions to the basin), but it shows a decreasing sequence of maxima, which can be linked to the interplay between a decrease in precipitation since the 1980s and the reduction of ice melt. If glaciers in the basin were in equilibrium with the climate of the last two decades, their volume would be reduced to 81 ± 38 % of the year 2000 volume, and glacier runoff during dry periods would be 61 ± 24 % of its maximum contribution in the period 1955–2016, considerably decreasing the drought mitigation capacity of the basin.
... During daytime, cloud coverage was estimated by relating potential incoming solar radiation to actual recordings. Potential incoming clear-sky shortwave radiation is calculated following Corripio (2002), taking into account transmission losses due to scattering and absorption, multiple reflections between the atmosphere and the surface, and reflections and shading by the surrounding topography. Atmospheric transmissivity ( atm ) can then be computed as the ratio of actual and potential global radiation. ...
In this study, we assess the impact of forcing data errors, model structure, and parameter choices on 1-D snow simulations simultaneously within a global variance-based sensitivity analysis
framework. This approach allows inclusion of interaction effects, drawing a more representative picture of the resulting sensitivities. We utilize all combinations of a multiphysics snowpack model to mirror the
influence of model structure. Uncertainty ranges of model parameters and input data are extracted from the literature. We evaluate a suite of 230,000 model realizations at the snow monitoring station Kühtai (Tyrol, Austria, 1,920 m above sea level) against snow water equivalent observations. The results show throughout the course of 25 winter seasons (1991–2015) and different model performance criteria a large influence of forcing data uncertainty and its interactions on the model performance. Mean interannual total sensitivity indices are in the general order of parameter choice < model structure < forcing error, with precipitation, air temperature, and the radiative forcings controlling the variance during the accumulation period and air temperature and longwave irradiance controlling the variance during the ablation period, respectively. Model skill is highly sensitive to the snowpack liquid water transport scheme throughout the whole winter period and to albedo representation during the ablation period. We found a sufficiently long evaluation period ( > 10 years) is required for robust averaging. A considerable interaction effect was revealed, indicating that an improvement in the knowledge (i.e., reduction of uncertainty) of one factor alone might not necessarily improve model results.
... Past studies of its icy shell have envisioned a surface that is smooth at the lander scale, dominated by diffusive impact processes such as impact gardening and sputtering by charged particles in Jupiter's magnetic field [4][5][6][7][8][9][10] . However, on Earth, icy surfaces ablated by solar radiation develop characteristic roughness patterns at the centimetre to multi-metre scale [11][12][13][14][15][16] . Here we show that under modern Europan conditions, sublimation processes driven by solar radiation flux are expected to dominate over diffusive processes in a band around the satellite's equator. ...
... Radiative modelling confirms that penitentes form by scattering and lensing of light on and into snow and ice 11,16 . A key factor controlling penitente formation is that the pit of the structure must ablate faster than the sidewalls; if the sidewalls ablate faster, an alternate bowl-like stable form known as a suncup may develop 13,15,16 . Penitente growth requires a daily low solar incidence angle, such that light strikes the walls of the blades at a high angle, and illuminates the floors of the pits 13,14 . ...
... A key factor controlling penitente formation is that the pit of the structure must ablate faster than the sidewalls; if the sidewalls ablate faster, an alternate bowl-like stable form known as a suncup may develop 13,15,16 . Penitente growth requires a daily low solar incidence angle, such that light strikes the walls of the blades at a high angle, and illuminates the floors of the pits 13,14 . This maximizes the contrast in flux per unit area on the floor compared to the sidewalls, both in terms of direct and scattered radiation 14 , and explains why terrestrial examples are usually found near the equator, or also on steep equatorwardfacing slopes at higher latitudes 23 . ...
On Earth, the sublimation of massive ice deposits at equatorial latitudes under cold and dry conditions in the absence of any liquid melt leads to the formation of spiked and bladed textures eroded into the surface of the ice. These sublimation-sculpted blades are known as penitentes. For this process to take place on another planet, the ice must be sufficiently volatile to sublimate under surface conditions and diffusive processes that act to smooth the topography must operate more slowly. Here we calculate sublimation rates of water ice across the surface of Jupiter’s moon Europa. We find that surface sublimation rates exceed those of erosion by space weathering processes in Europa’s equatorial belt (latitudes below 23°), and that conditions would favour penitente growth. We estimate that penitentes on Europa could reach 15 m in depth with a spacing of 7.5 m near the equator, on average, if they were to have developed across the interval permitted by Europa’s mean surface age. Although available images of Europa have insufficient resolution to detect surface roughness at the multi-metre scale, radar and thermal data are consistent with our interpretation. We suggest that penitentes could pose a hazard to a future lander on Europa. © 2018, The Author(s), under exclusive licence to Springer Nature Limited.
... Con lo que la velocidad del viento aumenta con la altura y depende de la rugosidad de la superficie. Siguiendo el mismo procedimiento planteado, se obtienen expresiones similares para q y θ que relacionen K s y K l respectivamente (Brutsaert, 1982;Corripio, 2002). ...
The Andean glaciers, due to their high variability to temperature and precipitation variations are of great interest for assessing climatic fluctuations. In this project, a hydro glaciological model was adapted to analyze the influence of meteorological conditions on the production of melting flow in glacier 12 of the Antisana volcano (4735-5705 masl, 1.68 Km2, 0 29'S). The fusion was calculated using a distributed surface energy balance (BESD), while the runoff was estimated by linear reservoirs including the moraine. The energy fluxes were simulated using 20 strips of height from the glacier snout to the summit at 30 minutes resolution in 684 days between 2011 and 2013 using meteorological measurements over the glacier at 4750 masl. The specific mass balance (-0.63 meters of water equivalent) (m we) and the ablation gradient (-2.13 m we (100m) -1) simulated agree with the estimates for tropical glaciers with altitude> 5400 masl, while the potential flow simulated (0.12 m3 s-1) reached to represent the hourly (r2 = 0.63) and daily (r2 = 0.6) variability of the observed. The months of high discharge ([0.17-0.22] m3 s-1) were related to the increase in temperature (> 1.5 C) and low precipitation (<40 mm) which increased the available energy. Conversely, the months of low discharge ([0.07-0.12] m3 s-1) were related to low temperatures (<0.8 C), high cloudiness and high precipitation (81 mm). This unpublished information for the site will allow estimating the rates of ablation and discharge in the glaciers located in the Eastern Cordillera of Ecuador.
... Lapse rates are either calculated from the point data in each time step or are pre-supplied as average monthly values. A radiation model based on the method by Corripio (2002) is used to calculate potential clear-sky solar radiation while taking into account terrain slope and orientation, hill shading, and transmission losses and gains due to scattering, absorption, and reflections, and it uses measured point values of global radiation to derive cloud factor fields and subsequently actual global radiation fields. Similarly, incoming longwave radiation is calculated using parameterizations for radiation received from the clear sky, clouds, and surrounding terrain. ...
A physically based hydroclimatological model (AMUNDSEN) is used to assess future climate change impacts on the cryosphere and hydrology of the Ötztal Alps (Austria) until 2100. The model is run in 100 m spatial and 3 h temporal resolution using in total 31 downscaled, bias-corrected, and temporally disaggregated EURO-CORDEX climate projections for the representative concentration pathways (RCPs) 2.6, 4.5, and 8.5 scenarios as forcing data, making this – to date – the most detailed study for this region in terms of process representation and range of considered climate projections. Changes in snow coverage, glacierization, and hydrological regimes are discussed both for a larger area encompassing the Ötztal Alps (1850 km², 862–3770 m a.s.l.) as well as for seven catchments in the area with varying size (11–165 km²) and glacierization (24–77 %).
Results show generally declining snow amounts with moderate decreases (0–20 % depending on the emission scenario) of mean annual snow water equivalent in high elevations (> 2500 m a.s.l.) until the end of the century. The largest decreases, amounting to up to 25–80 %, are projected to occur in elevations below 1500 m a.s.l. Glaciers in the region will continue to retreat strongly, leaving only 4–20 % of the initial (as of 2006) ice volume left by 2100. Total and summer (JJA) runoff will change little during the early 21st century (2011–2040) with simulated decreases (compared to 1997–2006) of up to 11 % (total) and 13 % (summer) depending on catchment and scenario, whereas runoff volumes decrease by up to 39 % (total) and 47 % (summer) towards the end of the century (2071–2100), accompanied by a shift in peak flows from July towards June.
