No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Glacial Landforms and the Age of Deglaciation in the Tiksi Area, East Siberia
Abstract
Tiksi area in eastern Siberia has generally been believed to have remained ice-free throughout the entire Ice Age. However, new glacial geomorphological research in the region has revealed evidence of a former ice sheet centered on the East Siberian shelf and reaching as far as Tiksi Bay. Among indications supporting this concept are fresh-looking U-shaped valleys, giant flutes, rock drumlins and other ice-erosional features, as well as systems of glaciotectonic ridges coupled with rock basins ("hill-and-hole pairs")--all attesting to a former ice motion in a northeast-southwest direction. The work carried out in May 1990 by a Swedish-Soviet field party was aimed at resolving the chronology of the latest glacial events in the Tiksi area. To this end, the bottom sediments of two lakes joined by glaciotectonic ridges were cored, analysed and AMS-14C dated. The ages of 6450+/-110 6870+/-80 and 8500+/-160 radiocarbon years BP were minimum dates obtained for the beginning of lacustrine sedimentation in the basins. This suggested that the last icesheet glaciation of the area had been of Late Pleistocene age.
... Paleobotanical studies throughout Siberia have indicated that climatic warming commenced during the early Holocene, and reached a thermal maximum during the mid-Holocene (ca. 6500 yr BP) (Khotinskiy, 1984;Grosswald et al., 1992;Peteet et al., 1998). Pollen data, together with dated buried larch wood, have provided evidence for the expansion of the forest zone 100 to 150 km north of its former position during the early to mid-Holocene. ...
... Pollen data, together with dated buried larch wood, have provided evidence for the expansion of the forest zone 100 to 150 km north of its former position during the early to mid-Holocene. This migration is thought to be the result of a warmer, more humid, and less continental climate (Khotinskiy, 1984;Grosswald et al., 1992). A change to a cooler and drier climate during the Late Holocene (ca. ...
Diatoms and other siliceous microfossils were examined from a 386-cm-long peat core, covering the last ca. 7200 yr, from north-central Siberia to gain insights into peatland developmental history, and to explore the potential of diatoms as proxy indicators in arctic peats. Diatom analyses of arctic peatlands are rare, and so one aspect of this study was to examine the sensitivity of diatom taxa in relation to independent paleoindicators already described from this core. Changes in the relative abundances of diatom taxa divided the core into four zones that closely tracked the ontogeny of the peatland from an open water environment (Zone I: benthic, alkaliphilic taxa), followed by fen environments (Zones II and III; epiphytic, acidophilic taxa), and finally to a better-drained, high-centered bog (Zone IV; aerophilic taxa). In addition to the diatom taxa, observations were made on the relative abundances of siliceous protozoan plates, chrysophyte cysts, and phytoliths. Both the diatoms and these other siliceous microfossils appeared to respond to changes in hydrology and moisture, as well as to fire episodes likely triggered by climatic change. This study demonstrates that diatoms and other siliceous microfossils from arctic peat deposits provide an important source of paleoenvironmental information that can strengthen interpretations derived from other commonly used indicators.
... It fits well into the context of Eurasia's Late Weichselian pale- oglaciology [Bintanja et al., 2002; Grosswald and Hughes, 2002], as well as was supported by several climate-based modeling experiments [e.g., Budd et al., 1998]. Moreover, it goes along with new geological evidence, such as ice-shoved features of Tiksi area [Grosswald and Spektor, 1993; Grosswald et al., 1992] and the Kolyma River-delta [Grosswald, 1996] , with the assemblages of oriented lake-and-ridge landform of Arctic coastal plains and with submarine grooves and recessional moraines of Chukchi Borderland uncovered by Polyak et al. [2001]. Nevertheless, to me, the model looks somewhat " narrowminded " , it focuses on some facets of the Arctic ice age but disregards the others, as important facets. ...
... We are aware of a wealth of geomorphic evidence attesting to forceful glacial advances from the heart of the Arctic toward Central and East Siberia as well as to Beringia and further south into the North Pacific. In particular, there is aforementioned evidence for Pleistocene north-to-south ice thrusting in the wide area between the Kara Sea [Polyak et al., 2002], the New Siberian Islands (Figures 6, 7) [Grosswald, 1988a [Grosswald, , 1988b [Grosswald, , 1989, Tiksi Harbour (Figure 8 ) [Grosswald and Spektor, 1993; Grosswald et al., 1992] and the lower Yana, Indigirka and Kolyma River basins [Grosswald, 1996] (Figure 9 ). There is as conclusive evidence for glacial overriding of Chukchi Peninsula from the north as well [Grosswald, 1998; Grosswald and Hughes, 2002]. ...
Early in the XIX century, the founders of glacial theory conceived of a "polar ice cap" centered on the North Pole and extending as far south as central Europe. However later this model was discarded. The deep Arctic Ocean, discovered in 1890s, was thought inconsistent with the model. Moreover, a belief took hold that the Arctic was not more severely glacierized than now, as polar snowfall seemed insucient to nourish much bigger ice masses. So the reigning concept of the XX century suggested that the past great ice sheets of Northern Hemisphere had mostly located on the mid-latitude continents. This concept was first challenged in 1970s, when Hughes et al. (1977) put forth the model of an Arctic Ice Sheet (AIS) that had formed largely in the Arctic Ocean. A core ice-shelf mechanism of Arctic Ice Sheet formation was proposed, which suggested: first, an inception of ice shelves in confined cold-water seas; second, turning the ice shelves into marine ice domes grounded on the polar continental shelves; and third, amalgamation of the Arctic terrestrial, marine-based, and floating ice components into a single Antarctic-style dynamic system. Now, a marine ice transgression hypothesis is proposed which suggests that the Arctic marine ice domes and thick floating ice shelf would push outwards and transgress onto adjacent lands. The Arctic Ice Sheet was an unstable, threshold-like system, prone to generate nonlinear responses to gradual change in forcing. The responses materialized in glacial surges, Heinrich events, and megafloods. As a result of the Earth's rotation, the system developed a west-to-east asymmetry.
... Pollen data, together with dated buried larch wood, have provided evidence for the expansion of the forest zone 100 to 150 km north of its former position during the early to mid-Holocene. This migration is thought to be the result of a warmer, more humid, and less continental climate (Khotinskiy, 1984;Grosswald et al., 1992). A change to a cooler and drier climate during the Late Holocene (ca. ...
Diatoms and other siliceous microfossils were examined from a 386-cm-long peat core, covering the last ca. 7200 yr, from north-central Siberia to gain insights into peatland developmental history, and to explore the potential of diatoms as proxy indicators in arctic peats. Diatom analyses of arctic peatlands are rare, and so one aspect of this study was to examine the sensitivity of diatom taxa in relation to independent paleoindicators already described from this core. Changes in the relative abundances of diatom taxa divided the core into four zones that closely tracked the ontogeny of the peatland from an open water environment (Zone I: benthic, alkaliphilic taxa), followed by fen environments (Zones II and III; epiphytic, acidophilic taxa), and finally to a better-drained, high-centered bog (Zone IV; aerophilic taxa). In addition to the diatom taxa, observations were made on the relative abundances of siliceous protozoan plates, chrysophyte cysts, and phytoliths. Both the diatoms and these other siliceous microfossils appeared to respond to changes in hydrology and moisture, as well as to fire episodes likely triggered by climatic change. This study demonstrates that diatoms and other siliceous microfossils from arctic peat deposits provide an important source of paleoenvironmental information that can strengthen interpretations derived from other commonly used indicators.
... At the EC mast, air temperatures follow temperatures measured at the climatological station closely. Bedrock in the site is composed of alkaline sandstone, mudstone and shale, and the soil is continuous, deep permafrost (Grosswald et al., 1992). Seasonal fluctuations of temperature at the upper soil layer (0-40 cm, measured using individually calibrated PT100 sensors) follow fluctuations in air temperature ( Fig. 1), but this pattern also markedly varies within the landscape. ...
Arctic tundra ecosystems will play a key role in future climate change due to
intensifying permafrost thawing, plant growth and ecosystem carbon exchange,
but monitoring these changes may be challenging due to the heterogeneity of
Arctic landscapes. We examined spatial variation and linkages of soil and
plant attributes in a site of Siberian Arctic tundra in Tiksi, northeast
Russia, and evaluated possibilities to capture this variation by remote
sensing for the benefit of carbon exchange measurements and landscape
extrapolation. We distinguished nine land cover types (LCTs) and to
characterize them, sampled 92 study plots for plant and soil attributes in
2014. Moreover, to test if variation in plant and soil attributes can be
detected using remote sensing, we produced a normalized difference vegetation
index (NDVI) and topographical parameters for each study plot using three
very high spatial resolution multispectral satellite images. We found that
soils ranged from mineral soils in bare soil and lichen tundra LCTs to soils
of high percentage of organic matter (OM) in graminoid tundra, bog, dry fen
and wet fen. OM content of the top soil was on average 14 g dm−3 in bare
soil and lichen tundra and 89 g dm−3 in other LCTs. Total moss biomass
varied from 0 to 820 g m−2, total vascular shoot mass from 7 to 112 g m−2
and vascular leaf area index (LAI) from 0.04 to 0.95 among LCTs. In
late summer, soil temperatures at 15 cm depth were on average 14 °C in bare soil and lichen tundra, and varied from 5 to 9 °C in
other LCTs. On average, depth of the biologically active, unfrozen soil layer
doubled from early July to mid-August.
When contrasted across study plots,
moss biomass was positively associated with soil OM % and OM content and
negatively associated with soil temperature, explaining 14–34 % of
variation. Vascular shoot mass and LAI were also positively associated with
soil OM content, and LAI with active layer depth, but only explained 6–15 %
of variation. NDVI captured variation in vascular LAI better than in
moss biomass, but while this difference was significant with late season
NDVI, it was minimal with early season NDVI. For this reason, soil attributes
associated with moss mass were better captured by early season NDVI.
Topographic attributes were related to LAI and many soil attributes, but not
to moss biomass and could not increase the amount of spatial variation
explained in plant and soil attributes above that achieved by NDVI. The LCT
map we produced had low to moderate uncertainty in predictions for plant and
soil properties except for moss biomass and bare soil and lichen tundra LCTs.
Our results illustrate a typical tundra ecosystem with great fine-scale
spatial variation in both plant and soil attributes. Mosses dominate plant
biomass and control many soil attributes, including OM % and temperature,
but variation in moss biomass is difficult to capture by remote sensing
reflectance, topography or a LCT map. Despite the general accuracy of
landscape level predictions in our LCT approach, this indicates challenges in
the spatial extrapolation of some of those vegetation and soil attributes
that are relevant for the regional ecosystem and global climate models.
... At the EC mast, air temperatures follow temperatures measured at the climatological station closely. Bedrock in the site is composed of alkaline sandstone, mudstone and shale, and the soil is in continuous, deep permafrost (Grosswald et al., 1992). Seasonal fluctuations of temperature at the upper soil layer (0-40 cm, measured using individually calibrated PT100 sensors) follow fluctuations in air temperature ( Fig. 1), but this pattern also markedly varies within the landscape. ...
Arctic tundra ecosystems will have a key role in future climate change due to intensifying permafrost thawing, plant growth and ecosystem carbon exchange, but monitoring these changes may be challenging due to the heterogeneity of Arctic landscapes. We examined spatial variation and linkages of soil and plant attributes in a site of Siberian Arctic tundra in Tiksi, northeast Russia, and evaluated possibilities to capture this variation by remote sensing for the benefit of carbon exchange measurements and landscape extrapolation. We distinguished nine land cover types (LCTs) – bare soil, lichen tundra, shrub tundra, flood meadow, graminoid tundra, bog, dry fen, wet den and water – to classify the variation in our site. To characterize the LCTs, we sampled 92 study plots for plant (biomass and leaf area index, LAI) and soil (organic matter OM%, bulk density, moisture, pH, litter layer depth, litter mass loss, temperature and active layer depth) attributes in 2014. Moreover, to test if variation in plant and soil attributes can be detected using remote sensing, we produced a normalized difference vegetation index (NDVI) and topographical parameters for each study plot using three very high spatial resolution multispectral satellite images (QuickBird and WorldView-2, portraying vegetation at 180, 220 and 750 growing degree days, DD with 0 °C threshold) and a digital elevation model (derived from a WV-2 stereo-pair image). We found that soils in our site ranged from mineral soils in bare soil and lichen tundra (on average 3.9 % OM) to soils of high OM% in graminoid tundra, bog, dry fen and wet fen (38 %), with shrub tundra and flood meadow being intermediate (21 %). Soil OM content was on average 14 g dm−3 in bare soil and lichen tundra and 89 g dm−3 in other LCTs. Total moss biomass varied from 0 to 820 g m−2 among LCTs and high moss mass was associated with high soil OM%, except that wet fens with high OM% sustained low moss mass. Total vascular shoot mass was 7 g m−2 in bare soil, on average 53 g m−2 in lichen tundra and dry fen and 91 g m−2 in other LCTs. Vascular LAI was on average 0.12 in bare soil and lichen tundra, 0.50 in bog, dry fen, shrub tundra and graminoid tundra, and 0.90 in flood meadow and wet fen. In late summer, soil temperatures at 15 cm depth were on average 14 °C in bare soil and lichen tundra, 9 °C in flood meadow and wet fen and 6 °C in other LCTs. Depth of the active soil layer doubled from early July to middle August, when it reached on average 42 cm in flood meadow and wet fen, 35 cm in bog, dry fen and graminoid tundra and 26 cm in bare soil and lichen and shrub tundra. When contrasted across study plots, total moss biomass was positively associated with soil OM% and OM content and negatively with soil temperature, explaining 14–34 % of variation in soil attributes. Vascular shoot mass and LAI were also positively associated with soil OM content, and LAI with active layer depth, but the amount of variation explained was significantly lower (6–15 %). NDVI captured variation in peak season vascular LAI better than variation in moss biomass, but the difference depended on the phase of the growing season in the image: 180-DD, 220-DD and 750-DD NDVI captured 23, 17 and 7 % of moss mass variation and 25, 34 and 50 % of vascular LAI variation, respectively. For this reason, soil attributes associated with moss mass were better captured by early season NDVI and those associated with LAI by late season NDVI. Topographic attributes were related to LAI and many soil attributes, but not to moss biomass and they could not increase the amount of spatial variation explained in plant and soil attributes above that achieved by NDVI. Our results illustrate a typical tundra ecosystem with great fine-scale spatial variation in both plant and soil attributes. Mosses dominate plant biomass and control many soil attributes, including OM% and temperature, but variation in moss biomass is difficult to capture by remote sensing reflectance or topography. This suggests that using simple reflectance indices and DEM for spatial extrapolation of those vegetation and soil attributes that are relevant for regional ecosystem and global climate models warrants further inspection. Meanwhile, land cover maps of LCTs and their attributes, derived from remote sensing data and effective field sampling in different LCTs, seem to provide the most reliable way to extrapolate vegetation and soil properties within Arctic tundra landscapes.
... Thus, both congruence across different taxa and concordance across different gene genealogies within Lemmus, support the significance of historical separation in the Lena river area. Although the extent of the Pleistocene glaciation was limited in this part of the Siberian Arctic, an ice sheet on the Verkhoyansky Mountain Ridge (Andersen & Borns, 1997), in combination with the ice sheet centered on the East Siberian shelf (Grosswald et al., 1992) might be the cause of the historical barrier at the Lena. The 4.3% of the cyt b sequence divergence across the river suggests that separation between the Western and the Central phylogeographic groups occurred prior to. the last glaciation (Weichsel, 1 15-10 kyr BP, Andersen & Borns, 1997). ...
The geographic pattern of mtDNA variation in lemmings from 13 localities throughout the Eurasian Arctic was studied by using eight restriction enzymes and sequencing of the cytochromebregion. These data are used to reveal the vicariant history ofLemmus, and to examine the effect of the last glaciation on mtDNA variation by comparing diversity in formerly glaciated areas to the diversity in non-glaciated areas. Phylogenetic congruence across different Arctic taxa and association between observed discontinuities, and probable Pleistocene barriers, suggest that glacial-interglacial periods were crucial in the vicariant history ofLemmus. Differences in amount of divergence (2.1–9.1%) across different historical barriers indicate chronologically separate vicariant events during the Quaternary. Populations from a formerly glaciated area are no less variable than those in the non-glaciated area. Regardless of glaciation history, no population structure and high haplotype diversity were found within geographic regions. The lack of population structure indicates that populations with high ancestral haplotype diversity shifted their distribution during the Holocene, and that lemmings tracked a changing environment during the Quaternary without reduction of effective population size.
... Thus, both congruence across different taxa and concordance across different gene genealogies within Lemmus, support the significance of historical separation in the Lena river area. Although the extent of the Pleistocene glaciation was limited in this part of the Siberian Arctic, an ice sheet on the Verkhoyansky Mountain Ridge (Andersen & Borns, 1997), in combination with the ice sheet centered on the East Siberian shelf (Grosswald et al., 1992) might be the cause of the historical barrier at the Lena. The 4.3% of the cyt b sequence divergence across the river suggests that separation between the Western and the Central phylogeographic groups occurred prior to. the last glaciation (Weichsel, 1 15-10 kyr BP,Andersen & Borns, 1997). ...
The geographic pattern of mtDNA variation in lemmings from 13 localities throughout the Eurasian Arctic was studied by using eight restriction enzymes and sequencing of the cytochrome b region. These data are used to reveal the vicariant history of Lemmus, and to examine the effect of the last glaciation on mtDNA variation by comparing diversity in formerly glaciated areas to the diversity in non‐glaciated areas. Phylogenetic congruence across different Arctic taxa and association between observed discontinuities, and probable Pleistocene barriers, suggest that glacial‐interglacial periods were crucial in the vicariant history of Lemmus. Differences in amount of divergence (2.1–9.1%) across different historical barriers indicate chronologically separate vicariant events during the Quaternary. Populations from a formerly glaciated area are no less variable than those in the non‐glaciated area. Regardless of glaciation history, no population structure and high haplotype diversity were found within geographic regions. The lack of population structure indicates that populations with high ancestral haplotype diversity shifted their distribution during the Holocene, and that lemmings tracked a changing environment during the Quaternary without reduction of effective population size.
... Grosswald and Hughes (2002) suggested the largest glaciation in the area, with an ice cap up to 2000 m high, was centered in the Yana Highlands during the late Weichselian. The ice cap was part of a large pan-Arctic ice sheet (see also Grosswald et al., 1992;Grosswald and Spektor, 1993;Grosswald, 1998). However, the hypothesis of such a large arctic ice sheet has been seriously challenged in recent years (e.g., Sher, 1995;Svendsen et al., 1999Svendsen et al., , 2004Karhu et al., 2001;Spielhagen, 2001;Gualtieri et al., 2000Gualtieri et al., , 2003. ...
Geomorphological mapping revealed five terminal moraines in the central Verkhoyansk Mountains. The youngest terminal moraine (I) was formed at least 50ka ago according to new IRSL (infrared optically stimulated luminescence) dates. Older terminal moraines in the western foreland of the mountains are much more extensive in size. Although the smallest of these older moraines, moraine II, has not been dated, moraine III is 80 to 90ka, moraine IV is 100 to 120ka, and the outermost moraine V was deposited around 135ka. This glaciation history is comparable to that of the Barents and Kara ice sheet and partly to that of the Polar Ural Mountains regarding the timing of the glaciations. However, no glaciation occurred during the global last glacial maximum (MIS 2). Based on cirque orientation and different glacier extent on the eastern and western flanks of the Verkhoyansk Mountains, local glaciations are mainly controlled by moisture transport from the west across the Eurasian continent. Thus glaciations in the Verkhoyansk Mountains not only express local climate changes but also are strongly influenced by the extent of the Eurasian ice sheets.
... There has been debate regarding the extent of these glaciations and the existence or not of a panarctic ice sheet covering northeastern Siberia. Grosswald et al. (1992) argue for the existence of a panarctic ice sheet and cite accelerator mass spectometry ages of 6400-8500 BP from basal lake sediments as minimum ages for late deglaciation. However, mammoth remains found in the Tiksi area, and radiocarbon dated at 21 600 BP, effectively refute the panarctic ice sheet hypothesis (Sher 1995). ...
A 3.86 m core of peat and organic lake mud from a polygonal peatland in the Lena River valley of Siberia was radiocarbon dated and analyzed for pollen, plant macrofossils, chrysophyte stomatocysts, stable isotopes, and charcoal. At around 7200 BP, a shallow lake or open-water wetland supported diverse aquatic macrophytes. The site had transformed initially into a richer fen with Carex, Comarum palustris, and Drepanocladus and later a poorer fen with Sphagnum which persisted until around 3000 BP. Fire may have been responsible for silt being blown onto the peatland, which changed the hydrological and geochemical conditions for development of the poor fen. Ice accretion led to an increase in the height of the centre of the polygon and expansion of Sphagnum peatland . 18O values become progressively more enriched, which reflects more direct input of summer precipitation waters and less groundwater during this period. Finally, the peatland surface was elevated sufficiently to limit water and nutrient supply, thereby allowing Ericaceae and Betula to grow at the coring site. Fire burned the peatland surface and may have exaggerated the extremely slow rate of peat accumulation. Fire may also be a factor in maintaining the open Larix dahurica forest in the region today, while climate may be contributing to reducing postfire regeneration. Fire and climate together may be controlling the character and composition of forests near tree line in the Lena River valley of this part of Siberia.
... No traces of glacial processes or deposits (tills) have been found. These observations contradict the idea that ice sheets expanded into this region (Grosswald et al., 1992) and agree with the notion of persisting periglacial environments (Faustova and Velichko, 1992; Tomirdiaro, 1993). Thus, the study area can truly be considered a part of unglaciated Beringia. ...
In order to reconstruct the Late- and Postglacial vegetation history of the northwestern edge of Beringia, a sediment core was collected from a lake north of the present treeline along the lower Lena River of northeastern Siberia, and analysed for fossil pollen and stomates. In addition, fossil tree stumps were collected in the vicinity of the lake. Eight radiocarbon dates indicate that the lake sediment record spans at least the past 12,300yrBP. The early vegetation at this site was dominated by herb and shrub tundra. Possible evidence of Younger Dryas cooling, consisting of a decrease in shrub birch and increases in grass and herbaceous plants, occurs between 11,000 and 10,000yr BP. Forests, dominated by Larix dahurica and including Picea obovata, extended northward to the site between 8500 and 3500yr BP. There is an agreement between the pollen, stomate and tree stump evidence for this advance. The modern vegetation of shrub tundra was established after 3500yr BP.
The paleoglaciological concept that during the Pleistocene glacial hemi-cycles a super-large, structurally complex ice sheet developed in the Arctic and behaved as a single dynamic system. as the Antarctic ice sheet does today, has not yet been subjected to concerted studies designed to test the predictions of this concept. Yet, it may hold the keys to solutions of major problems of paleoglaciology, to understanding climate and sea-level changes. The Russian Arctic is the least-known region exposed to paleoglaciation by a hypothetical Arctic ice sheet but now it is more open to testing the concept. Implementation of these tests is a challenging task, as the region is extensive and the available data are controversial. Well-planned and coordinated field projects are needed today, as well as broad discussion of the known evidence, existing interpretations and new field results. Here we present the known evidence for paleoglaciation of the Russian Arctic continental shelf and reconstruct possible marine ice sheets that could have produced that evidence.
The Taymyr Peninsula constitutes the eastern delimitation of a possible Kara Sea basin ice sheet. The existence of such an ice sheet during the last global glacial maximum (LGM), i.e. during the Late Weichselian/Upper Zyryansk, is favoured by some Russian scientists. However, a growing number of studies point towards a more minimalistic view concerning the areal extent of Late Weichselian/Upper Zyryansk Siberian glaciation. Investigations carried out by us along the central Byrranga Mountains and in the Taymyr Lake basin south thereof, reject the possibility of a Late Weichselian/Upper Zyryansk glaciation of this area. Our conclusion is based on the following: Dating of a continuous lacustrine sediment sequence at Cape Sabler on the Taymyr Lake shows that it spans at least the period 39–17 ka BP. Even younger ages have been reported, suggesting that this lacustrine environment prevailed until shortly before the Holocene. The distribution of these sediments indicates the existence of a paleo-Taymyr lake reaching c. 60 m above present sea level. A reconnaissance of the central part of the Byrranga Mountains gave no evidence of any more recent glacial coverage. The only evidence of glaciation — an indirect one — is deltaic sequences around 100–120 m a.s.l., suggesting glacio-isostatic depression and a large input of glacial meltwater from the north. However, 14C and ESR datings of these marine sediments suggest that they are of Early Weichselian/Lower Zyryansk or older age. As they are not covered by till and show no glaciotectonic disturbances, they support our opinion that there was no Late Weichselian/Lower Zyryansk glaciation in this area. We thus suggest that the Taymyr Peninsula was most probably glaciated during the early part of the last glacial cycle (when there was only small- to mediumscale glaciation in Scandinavia), but not glaciated during the later part of that cycle (which had the maximum ice-sheet coverage over north-western Europe). This fits a climatic scenario suggesting that the Taymyr area, like most of Siberia, would come into precipitation shadow during times with large-scale ice-sheet coverage of Scandinavia and the rest of north-western Europe.
Paleoglaciology deals with glaciation cycles of the Quaternary Ice Age.
It combines the dynamics of present-day ice sheets deduced from
glaciology with the history of former ice sheets deduced from glacial
geology. Cosmogenic dating now makes a detailed chronology of a cycle
possible. Radiocarbon dating has provided a detailed chronology for
Termination of the last cycle, but cannot date how the cycle began. Here
we identify the central challenge in applying paleoglaciology to
Quaternary glaciation cycles in general, and initiation of these cycles
in particular. The challenge is the role of thickening sea ice in the
Arctic Ocean, possibly becoming thick ice shelves floating over deep
Arctic basins and high marine ice sheets grounded on shallow Arctic
continental shelves. In that case, an Arctic Ice Sheet existed that was
larger and less stable than the Antarctic Ice Sheet is now or in the
past. Two approaches to this problem are presented as Part 1 and Part 2.
In Part 1, the height of these former ice sheets is linked primarily to
the strength of ice-bed coupling, which is deduced from glacial geology.
It provides "snapshots" of ice sheets that give ice elevations
independent of the past history and largely independent of ice-surface
conditions, temperatures and the mass balance in particular. In Part 2,
heights of former ice sheets depend on both their past history,
particularly initial conditions, and changing surface conditions during
the glaciation cycle. This provides a "motion picture" of ice sheets
during the full cycle. The challenge is to establish a "mind meld" of
these two approaches. They allow new perspectives on paleoglaciology.
The paleoglaciological concept that during the Pleistocene glacial hemi-cycles a super-large, structurally complex ice sheet developed in the Arctic and behaved as a single dynamic system, as the Antarctic ice sheet does today, has not yet been subjected to concerted studies designed to test the predictions of this concept. Yet, it may hold the keys to solutions of major problems of paleoglaciology, to understanding climate and sea-level changes. The Russian Arctic is the least-known region exposed to paleoglaciation by a hypothetical Arctic ice sheet but now it is more open to testing the concept. Implementation of these tests is a challenging task, as the region is extensive and the available data are controversial. Well-planned and coordinated field projects are needed today, as well as broad discussion of the known evidence, existing interpretations and new field results. Here we present the known evidence for paleoglaciation of the Russian Arctic continental shelf and reconstruct possible marine ice sheets that could have produced that evidence.
Drumlin relief is a key parameter for testing predictions of models of drumlin formation. Although this metric is commonly described in textbooks as being of the order of a few tens of metres, our critical review of the literature suggests an average value of about 13 m, but with much uncertainty. Here we investigate a large sample of drumlins (25,848) mapped from a high resolution digital terrain model of Britain, which allowed the identification of extremely shallow drumlins. Results indicate that most drumlins have a relief between 0.5 and 40 m (with a surprisingly low average value of only 7.1 m) a mode of 3.5–4 m, and with 41% of all drumlins characterized by a relief < 5 m. Drumlin relief is found to never exceed 7% of the width and is positively correlated with this parameter, possibly indicating that drumlins need a large base to stand against the flow of the ice. Drumlin relief is also positively correlated with the length, which shows that drumlins do not grow in length by redistributing sediments from their summits to their downflow (lee) end, as previously hypothesised.
Oriented assemblages of parallel ridges and elongated lakes are widespread on the coastal lowlands of northeast Eurasia and Arctic North America, in particular, in Alaska, Arctic Canada, and northeast Siberia. So far, only the oriented lakes have been of much scientific interest. They are believed to be formed by thermokarst in perennially frozen ice-rich sediments, while their orientation is accounted for either by impact of modern winds blowing at right angles to long axes of the lakes (when it concerns individual lakes), or by the influence of underlying bedrock structures (in the case of longitudinal and transverse alignment of lake clusters).
En masse examination of space images suggests that oriented lake-and-ridge assemblages, not the oriented lakes alone, occur in the Arctic. Hence any theory about their formation should account for the origin and orientation of the assemblages as a whole. The existing hypotheses appear inadequate for this end, so this paper proposes that the assemblages were initially created by glacial activity, that is, by ice sheets that drumlinized and tectonized their beds, as well as by sub- and proglacial meltwater, and then they were modified by thermokarst, solifluction, and aeolian processes. This assumption opens up an avenue by which all known features of oriented landforms in the Arctic can be explained. The paper suggests that the oriented landforms in Siberia and Alaska are largely signatures of a marine Arctic ice sheet that transgressed from the north, while the Baffin Island and Mackenzie Delta forms were created by the respective sectors of the Laurentide ice sheet. The oriented features discussed belong to the last Late Glacial through the Early Holocene.
Analysis of midge remains in late-Quaternary sediment, recovered from a lake situated north of treeline in northeast Siberia, indicates the occurrence of notable climatic fluctuations during the last 12 ka. The onset of late-glacial warming was disrupted by a marked cooling event – possibly correlative with the Younger Dryas – that occurred between 11,000 and 10,000 yr BP. Increases in the relative abundance of taxa typically found in tundra lakes, such as Hydrobaenus/Oliveridia and Parakiefferiella nigra, and the concurrent decrease in temperate taxa, such as Microtendipes and Corynocera ambigua, suggest climatic deterioration occurred during this interval. At approximately 10,000 yr BP there was a large increase in temperate taxa such as Microtendipes and C. ambigua, and a decline of essentially all cold-water taxa. This suggests that climate was warmer than present since the modern distribution of both Microtendipes and C. ambigua is limited to forested sites in this region. This warm interval lasted until approximately 6000 yr BP when there was a precipitous decline in temperate chironomid taxa and an increase in cold-water chironomid taxa, such as Paracladius, Hydrobaenus/Oliveridia, Abiskomyia, and Parakiefferiella nigra. This cooling continued through the late-Holocene and the modern tundra chironomid assemblage developed by approximately 1400 yr BP.
Collared lemmings (Dicrostonyx) demonstrate extensive chromosome variation along their circumpolar distribution in the high Arctic. To reveal the history of this genus and the origin of chromosome races in the Palearctic, we studied the geographical pattern of mtDNA variation in lemmings from 13 localities by using eight tetranucleotide restriction enzymes. The main split in mtDNA phylogeny is at the Bering Strait and corresponds to the main chromosome division between the Beringian and the Eurasian groups of karyotypes. Nucleotide divergence estimate of 6.8% suggests that, despite the Bering Land Bridge, Palearctic and Nearctic forms have been separated since the mid-Pleistocene. Five distinct phylogenetic groups of mtDNA haplotypes, with average divergence of 1.5%, corresponding to geographical regions, were found along the Palearctic coast. Low nucleotide and haplotype diversity and a star-like phylogeny within phylogeographical groups of haplotypes suggest regional bottleneck events in the recent past, most probably due to warming events during the Holocene. There is congruence between phylogeographical pattern of mtDNA variation and geographical distribution of chromosome races; 69% of the total mtDNA variation is allocated among chromosome races. This congruence implies that historical events such as fragmentation and allopatric bottleneck events have been important for the origin of chromosome races. However, historical factors do not explain the fixed autosome fusions found to distinguish certain populations.
The purpose of this investigation is to encourage a fresh look at Pleistocene Beringia. Heretofore, flooding of Bering Strait has been cited as the only barrier to migration, with marine sea transgressions being a “sea gate” that closed off migration during glacial interstadials and interglaciations. However, the possibility exists that glacial advances were also barriers, with marine ice transgressions being an “ice gate” that closed off migration during glacial stadials and glacial maxima. This possibility proceeds from the Marine Ice Transgression Hypothesis (MITH), which states that marine ice sheets form on the broad Arctic continental shelf of Northern Hemisphere continents when sea ice thickens, grounds and domes in shallow water, and then transgresses landward as continental ice sheets and seaward as floating ice shelves (Hughes, 1987). Landward transgression is onto coastal lowlands. During Pleistocene glaciations, a marine ice sheeet extending from Spitsbergen to Greenland may have transgressed the circumpolar continental landmass at its lowest and narrowest gap, central Beringia, and calved into the Pacific Ocean.
Interpretation of Space images coupled with field data on glacial geomorphology and glacial geology of Northern Eurasia have provided compelling evidence for a continuous Late Weichselian ice sheet covering the entire Arctic margin of the continent. In addition to the Scandinavian ice sheet, three ice sheets of the same order — the Karan, East Siberian and Beringian — are identified within the major Eurasian ice sheet. Also, there is evidence and other considerations suggesting a former ice sheet in the Sea of Okhotsk.Ice-spreading centers of the ice sheets were situated on the continental shelves off the Siberian coasts, thus we can term the ice sheets ‘Siberian’. So far, the conventional stratigraphic approach to the problem of Siberian glaciation has proven fruitless and yielded nothing but uncertainty, while geomorphological studies have discovered a wealth of glacial landforms in Arctic Siberia. It was these landforms and their spacing that made the existence of former Siberian ice sheets evident.The East Siberian ice sheet rested on the shelves of the eastern Laptev and East Siberian Seas, and its flow was directed radially, including up the Yana and Indigirka Rivers. The Beringian ice sheet was grounded on the Chukchi-, Bering-, and Beaufort Sea shelves, overriding the Chukchi and Seward Peninsulas from the north and flowing through the Bering Strait. It was continued by a thick floating ice shelf buttressed by the submarine Aleutian-Commander Ridge. The Okhotsk ice sheet was grounded on the Okhotsk shelf. Specific gemorphic signatures of marine ice sheets — the ‘glacially cut corners’ — have been identified on all promontories jutting out into the Bering and Okhotsk Seas. The Beringian and Okhotsk ice sheets are consistent with the results of deep-sea drilling in the adjacent North Pacific during Leg 145 of D/V JOIDES Resolution.
The extent of Late Weichselian glaciation in Arctic Russia remains a problem. Our model of 1995–1998 suggests a continuous and long-lived ice sheet centered on the Kara Sea. Other reconstructions suggest a smaller and “diachronous” glaciation. The vast majority of dates support the model of restricted glaciation. We show that these dates are inconsistent with the geologic record of ice flow across the Kara-Barents divide, with second-order glacial geology of Kola Peninsula, and with evidence for glacial surges. They are also inconsistent with Late Weichselian climate of the Arctic, with Eurasian continental paleohydrology, including meltwater drainage systems, cataclysmic megafloods, major transgressions of the Caspian Sea, and with the entire paleogeographic context of northern Eurasia. We believe that, due to impeded ventilation of the Pleistocene Arctic Ocean, these dates are often too old, and that recycling and contamination of the samples would also contribute to the dating errors. Destructive impacts of late-glacial ice-sheet surges and megafloods upon the Arctic glacial sequences would also aggravate the situation. By ignoring the dates until these problems are addressed, we find that the field evidence supports continuous glaciation of Arctic Russia at the LGM, and that the resulting ice sheet was part of an Arctic Ice Sheet that included an ice shelf in the Arctic Ocean and ice sheets in Greenland and North America. We present 3-D reconstructions of the Arctic Ice Sheet and, with an enlarged Antarctic Ice Sheet, we show that the ice volume is equivalent to an LGM sea level that was 130–135 m lower than at present. The reconstructions depict the Arctic Ice Sheet before and after massive thawing of the bed that allows partial gravitational collapse of the overlying ice, with a minimal change in ice volume.
Ice sheets flowing across a sedimentary bed usually produce a landscape of blister-like landforms streamlined in the direction of the ice flow and with each bump of the order of 102 to 103 m in length and 101 m in relief. Such landforms, known as drumlins, have mystified investigators for over a hundred years. A satisfactory explanation for their formation, and thus an appreciation of their glaciological significance, has remained elusive. A recent advance has been in numerical modelling of the land-forming process. In anticipation of future modelling endeavours, this paper is motivated by the requirement for robust data on drumlin size and shape for model testing.
ResearchGate has not been able to resolve any references for this publication.