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Based on radiocarbon dating, a tephra horizon, varve counts and palaeomagnetism, detailed age models covering the last ~24 k cal a bp, have been developed for the stratigraphy in the lakes Bolshoye Shchuchye and Maloye Shchuchye in the Polar Ural Mountains, Russia. The inclination curves from these lakes show nearly identical palaeomagnetic secular variations in the studied cores from both lakes, allowing for a precise correlation between the cores. A large and very distinct inclination deviation, named the Bolshoye Shchuchye Event, was identified in all cores retrieved from both lakes. It lasted over a period of 1245 years, from 20 470 to 19 225 cal a bp. The well-dated palaeomagnetic inclination graph offers a new possibility to correlate archives in this part of the Arctic for the last ~24 k cal a bp, probably also over longer distances. The sedimentation rate shows the same trend in all cores from both lakes, including high input during the Last Glacial Maximum and gradually lowering after ~18 k cal a bp to lower and stable Holocene values. publishedVersion

Understanding past responses of ice sheets to climate change provides an important long-term context for observations of present day, and projected future, ice-sheet change. In this work, we reconstruct the deglaciation of the marine-terminating western margin of the Scandinavian Ice Sheet in the outer Hardangerfjorden area of southwestern Norway, following the Last Glacial Maximum (LGM) until the start of the Holocene. We base our interpretations on a combination of geomorphological mapping using high-resolution (LiDAR) terrain models, 68 new cosmogenic nuclide 10Be exposure ages and radiocarbon-dated lake sediment cores, supported by the stratigraphic position of the 12.1 ka Vedde Ash. We show that even the highest mountain summits in the area (˜1200–1400 m a.s.l.) were ice-covered during the LGM, thus settling debates concerning the Scandinavian Ice Sheet thickness in this region. These summits emerged as nunataqs through the ice sheet about 22–18 ka, potentially owing to upstream ice thinning caused by the break-up and retreat of the Norwegian Channel Ice Stream. Following the break-up of the Norwegian Channel Ice Stream, the ice margin seemingly stabilized at the outermost coast for 3500–5500 years before the mouth of Hardangerfjorden became ice free at c. 14.5 ka. Subsequently, during the Bølling and Allerød periods, the ice sheet retreated rapidly into the inner parts of Hardangerfjorden before a major ice sheet re-advance during the Younger Dryas. We identify and reconstruct a sizeable, independent ice cap on the Ulvanosa mountain massif during the Younger Dryas (YD), a massif that earlier was mapped as covered by the Scandinavian Ice Sheet during the YD. We also document ice-free areas that are more extensive than previously thought between Hardangerfjorden and Matersfjorden during the YD. publishedVersion

Acknowledgements: Acknowledgements: We thank D. H. Mann for his detailed and constructive comments; and T. Ager, J. Austin, T. B. Brand, A. Cooper, S. Funder, M. T. P. Gilbert, T. Jørgensen, N. J. Korsgaard, S. Liu, M. Meldgaard, P. V. S. Olsen, M. L. Siggaard-Andersen, J. Stenderup, S. A. Woodroffe and staff at the GeoGenetics Sequencing Core and National Park Service-Western Arctic National Parklands for help and support. E.W. and D.J.M. thank the staff at St. John’s College, Cambridge, for providing a stimulating environment for scientific discussion of the project. E.W. thanks Illumina for collaboration. The Lundbeck Foundation GeoGenetics Centre is supported by the Carlsberg Foundation (CF18-0024), the Lundbeck Foundation (R302-2018-2155), the Novo Nordisk Foundation (NNF18SA0035006), the Wellcome Trust (UNS69906) and GRF EXC CRS Chair (44113220)—Cluster of Excellence. The PhyloNorway plant genome database is part of the Norwegian Barcode of Life Network (https://www.norbol.org) funded by the Research Council of Norway (226134/F50), the Norwegian Biodiversity Information Centre (14-14, 70184209) and The Arctic University Museum of Norway. Metabarcoding sequencing was funded by the Central Public-Interest Scientific Institution Basal Research Fund, CAFS (2017B001 and 2020A001). B.D.S. is supported by the Wellcome Trust programme in Mathematical Genomics and Medicine (WT220023); F.R. by a Villum Fonden Young Investigator award (no. 00025300); D.J.M. by the Quest Archaeological Research Fund; P.M. by the Swedish Research Council (VR); R.D. by the Wellcome Trust (WT207492); and A.R. by a Marie Skłodowska-Curie Actions Individual Fellowship (MSCA-IF, 703542) and the Research Council of Norway (KLIMAFORSK, 294929). L.O. has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (no. 681605); I.G.A. and Y.L. from the ERC under the European Union’s Horizon 2020 research and innovation programme (no. 819192). J.I.S. and J.M. are supported by the Research Council of Norway. P.B.H. and N.R.E. acknowledge NERC funding (grant NE/P015093/1). D.W.B. was supported by a Marie Skłodowska-Curie Actions Incoming International Fellowship (MCIIF-40974). T.S.K. is funded by a Carlsberg Foundation Young Researcher Fellowship (CF19-0712)., During the last glacial-interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1-8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across the Arctic spanning the past 50,000 years. Furthermore, we present 1,541 contemporary plant genome assemblies that were generated as reference sequences. Our study provides several insights into the long-term dynamics of the Arctic biota at the circumpolar and regional scales. Our key findings include: (1) a relatively homogeneous steppe-tundra flora dominated the Arctic during the Last Glacial Maximum, followed by regional divergence of vegetation during the Holocene epoch; (2) certain grazing animals consistently co-occurred in space and time; (3) humans appear to have been a minor factor in driving animal distributions; (4) higher effective precipitation, as well as an increase in the proportion of wetland plants, show negative effects on animal diversity; (5) the persistence of the steppe-tundra vegetation in northern Siberia enabled the late survival of several now-extinct megafauna species, including the woolly mammoth until 3.9 ± 0.2 thousand years ago (ka) and the woolly rhinoceros until 9.8 ± 0.2 ka; and (6) phylogenetic analysis of mammoth environmental DNA reveals a previously unsampled mitochondrial lineage. Our findings highlight the power of ancient environmental metagenomics analyses to advance understanding of population histories and long-term ecological dynamics.

A detailed, well-dated record of pollen and sedimentary ancient DNA (sedaDNA) for the period 15 000–9500 cal a bp describes changes at Lake Bolshoye Shchuchye in the Polar Ural Mountains, located far east of the classical Lateglacial sites in western Europe. Arctic tundra rapidly changed to lusher vegetation, possibly including both dwarf (Betula nana) and tree birch (B. pubescens), dated in our record to take place 14 565 cal a bp, coincident with the onset of the Bølling in western Europe; this was paralleled by increased summer temperatures. A striking feature is an early decline in Betula pollen and sedaDNA reads 300 years before the onset of the Younger Dryas (YD) in western Europe. Given the solid site chronology, this could indicate that the YD cooling started in Siberia and propagated westwards, or that the vegetation reacted to the inter-Allerød cooling at 13 100 cal a bp and did not recover during the late Allerød. During the YD, increases in steppe taxa such as Artemisia and Chenopodiaceae suggest drier conditions. At the onset of the Holocene, the vegetation around the lake reacted fast to the warmer conditions, as seen in the increase of arboreal taxa, especially Betula, and a decrease in herbs such as Artemisia and Cyperaceae. publishedVersion

The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26 000-19 000 years before present) – an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine δ18O proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80 000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and δ18O proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57 000-29 000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine δ18O and sea level may be more complex than assumed., The configuration of past ice sheets, and therefore sea level, is highly uncertain. Here, the authors provide a global reconstruction of ice sheets for the past 80,000 years that allows to test proxy based sea level reconstructions and helps to reconcile disagreements with sea level changes inferred from models.

A 24,000-year record of plant community dynamics, based on pollen and ancient DNA from the sediments (sedaDNA) of Lake Bolshoye Shchuchye in the Polar Ural Mountains, provides detailed information on the flora of the Last Glacial Maximum (LGM) and also changes in plant community composition and dominance. It greatly improves on incomplete records from short and fragmented stratigraphic sequences found in exposed sedimentary sections in the western Russian Arctic. In total, 162 plant taxa were detected by sedaDNA and 115 by pollen analysis. Several shifts in dominance between and within plant functional groups occurred over the studied period, but most taxa appear to have survived in situ. A diverse arctic-alpine herb flora characterised the interval ca. 24,000–17,000 cal years BP and persisted into the Holocene. Around 17,000 cal years BP, sedges (e.g. Carex) and bryophytes (e.g. Bryum, Aulacomnium) increased. The establishment of shrub-tundra communities of Dryas and Vaccinium sp., with potentially some Betula pubescens trees (influx ∼290 grains cm2 year−1), followed at ca. 15,000 cal years BP. Forest taxa such as Picea and ferns (e.g. Dryopteris fragrans, Gymnocarpium dryopteris) established near the lake from ca. 10,000 cal years BP, followed by the establishment of Larix trees from ca. 9000 cal years BP. Picea began to decline from ca. 7000 cal years BP. A complete withdrawal of forest tree taxa occurred by ca. 4000 cal years BP, presumably due to decreasing growing-season temperatures, allowing the expansion of dwarf-shrub tundra and a diverse herb community similar to the present-day vegetation mosaic. Contrary to some earlier comparative studies, sedaDNA and pollen from Lake Bolshoye Shchuchye showed high similarity in the timing of compositional changes and the occurrence of key plant taxa. The sedaDNA record revealed several features that the pollen stratigraphy and earlier palaeorecords in the region failed to detect; a sustained, long-term increase in floristic richness since the LGM until the early Holocene, turnover in grass and forb genera over the Pleistocene-Holocene transition, persistence of a diverse arctic-alpine flora over the late Quaternary, and a variable bryophyte flora through time. As pollen records are often limited by taxonomic resolution, differential productivity and dispersal, sedaDNA can provide improved estimates of floristic richness and is better able to distinguish between different plant assemblages. However, pollen remains superior at providing quantitative estimates of plant abundance changes and detecting several diverse groups (e.g. Poaceae, Cyperaceae, Asteraceae) which may be underreported in the sedaDNA. Joint use of the two proxies provided unprecedented floristic detail of past plant communities and helped to distinguish between long-distance transport of pollen and local presence, particularly for woody plant taxa.

While there are extensive macro- and microfossil records of a range of plants and animals from Quaternary records, earthworms and their close relatives among annelids are not preserved as fossils, and therefore we have limited knowledge of their Quaternary distributions. This lack of fossils means that clitellate worms (Annelida) are currently underused in palaeoecological research, even though they can provide valuable information about terrestrial and aquatic environmental conditions. Their DNA might be preserved in sediments, which offers an alternative method for detection. Here we analyse lacustrine sediments from lakes in the Polar Urals, Arctic Russia, covering the period 24,000-1,300 cal. years BP, and NE Norway (10,700-3,300 cal. years BP) using a universal mammal 16S rDNA marker. While mammals were recorded using the marker (reindeer was detected twice in the Polar Urals core at 23,000 and 14,000 cal. years BP, and four times in the Norwegian core at 11,000 cal. years BP and between 3,600-3,300 cal. years BP), worm extracellular DNA “bycatch” was rather high. In this paper we present the first reported worm detection from ancient DNA. Our results demonstrate that both aquatic and terrestrial clitellates can be identified in late-Quaternary lacustrine sediments, and the ecological information retrievable from this group warrants further research with a more targeted approach.

Tephra shards from the Vedde Ash eruption have been identified in two lakes from northwestern Russia and the Polar Ural Mountains. This is the most distal and easternmost occurrence of this regional tephra marker horizon found so far and it extends the area of the Vedde Ash tephra more than 1700 km further east than previously documented. This means that particles the size of fine sand have travelled more than 4000 km from the Katla volcano source, south Iceland. These findings offer a new possibility to correlate archives over a very long distance in the time period around the Younger Dryas. This work was financially supported by TheResearch Council of Norway and is a contribution to the project‘Climate History along the Arctic Seaboard of Eurasia’ (CHASE)(NRC 255415). The coring fieldwork was carried out in 2000 at LakeYamozero and 2009 at Lake Bolshoye Shchuchye during the formerresearch projects ‘Paleo Environment and Climate History of theRussian Arctic’ (PECHORA II) and ‘The Ice Age Development andHuman Settlement in Northern Eurasia’ (ICEHUS) funded by theResearch Council of Norway (NRC 167131 and NRC 176176048). M.Henriksen (Universityof Bergen)supplied the core material selected forthe Lake Yamozero cryptotephra detection work. The Lake Yamozerogeochemical analysis was conducted with funding from the NERCRAPID Climate Change thematic programme, project NE/C509158/1‘Precise chronology of the timing of changes in behaviour of the NorthAtlantic THC and their forcing effects, 16–8kaBP’.

Marine outlet glaciers on Greenland are retreating, yet it is unclear if the recent fast retreat will persist, and how atmosphere and ocean warming will impact future retreat. We show how a marine outlet glacier in Hardangerfjorden retreated rapidly in response to the abrupt warming following the Younger Dryas cold period (approximately 11,600 years before present). This almost 1000 m deep fjord, with several sills at 300–500 m depth, hosted a 175 km long outlet glacier at the western rim of the Scandinavian Ice Sheet. We use a dynamic ice-flow model constrained by well-dated terminal and lateral moraines to simulate the reconstructed 500-year retreat of Hardangerfjorden glacier. The model includes an idealized oceanic and atmospheric forcing based on reconstructions, but excludes the surface mass balance-elevation feedback. Our simulations show a highly episodic retreat driven by surface melt and warming fjord waters, paced by the fjord bathymetry. Warming air and ocean temperatures by 4–5 °C during the period of retreat result in a 125-km retreat of Hardangerfjorden glacier in 500 years. Retreat rates throughout the deglaciation vary by an order of magnitude from 50 to 2500 m a−1, generally close to 200 m a−1, punctuated by brief events of swift retreat exceeding 500 m a−1, each event lasting a few decades. We show that the fastest retreat rates occur in regions of the bed with the largest retrograde slopes; ice shelf length and fjord water depth is less important. Our results have implications for modern glacial fjord settings similar to Hardangerfjorden, where high retreat rates have been observed. Our findings imply that increasing air temperatures and warming subsurface waters in Greenland fjords will continue to drive extensive retreat of marine outlet glaciers. However, the recent high retreat rates are not expected to be sustained for longer than a few decades due to constraints by the fjord bathymetry. publishedVersion

The last deglaciation in northern Europe provides an opportunity to study the hydrologic component of abrupt climate shifts in a region with complex interactions between ice sheets and oceanic and atmospheric circulation. We use leaf wax hydrogen isotopes (δ2H) to reconstruct summer precipitation δ2H and aridity in southwestern Norway from 15.8 to 11.5 ka. We identify transitions to a more proximal moisture source before the ends of Heinrich Stadial 1 and the Younger Dryas, prior to local warming and increased primary productivity in both instances. We infer these changes in moisture delivery to southwestern Norway to be a response to northward shifts in the polar front caused by warm water intrusion into the North Atlantic, which preceded abrupt warming in the circum-North Atlantic. These results suggest that moisture transport pathways shift northward as warm surface ocean water reaches higher latitudes in the North Atlantic. publishedVersion

We reconstruct patterns of ice flow and retreat of the southwestern Scandinavian Ice Sheet, from 2900 field observations of glacial striae and elevation measurements of 60 ice-marginal-deltas from a high-resolution LiDAR DEM. During the Last Glacial Maximum, ice flow was towards the west across the entire area, including across several-hundred meter deep north-south oriented fjords. During deglaciation, ice flow adjusted to topography and the dominant flow direction switched towards the south-west. We use a shoreline diagram constructed from relative sea-level curves to establish the age of each delta, which allows us to constrain the timing of retreat with almost decadal precision. Rapid ice sheet retreat commenced at the onset of the Holocene at 11,600 cal years BP. Retreat rates were 160 m a −1 in the deepest fjords, 60–80 m a −1 in shallower fjords, and even slower for land-terminating margins. The fastest retreat rates, 240 m a −1 and 340 m a −1 , were experienced in the largest fjords, Hardangerfjorden and Sognefjorden, which border the study area to the south and north. Crosscutting glacial striae indicate that calving bays developed during retreat along the widest fjords. The combination of complex fjord topography with fast ice-margin retreat by iceberg calving, led to isolation of ice remnants on islands and peninsulas, a process that accelerated the overall rate of deglaciation. Ice-margin retreat paused between 11,300–11,100 cal years BP, probably due to cooling during the Preboreal Oscillation.

Cosmogenic nuclide exposure dating is a widely used method for constraining past ice sheet histories. We scrutinize a recently published data set of cosmogenic 10Be data from erratic boulders in Norway used to constrain the deglaciation of the western Scandinavian Ice Sheet to 20 ka. Our model of the 10Be inventory in glacial surfaces leads us to conclude that the chronology may be afflicted by the deep subsurface accumulation of 10Be during long-lasting ice-free periods that resulted in 10Be ages >10% too old. We suggest that the majority of the dated erratic boulders contain a uniform level of inherited muon-produced 10Be and were derived from bedrock depths >2.5 m and most likely ~4 m. The implication of our finding is that for landscapes that experience long ice-free periods between brief maximum glacial phases, glacial erosion of >5 m is required to remove detectable traces of inherited 10Be.

Marine-terminating glaciers and ice streams are important controls of ice sheet mass balance. However, understanding of their long-term response to external forcing is limited by relatively short observational records of present-day glaciers and sparse geologic evidence for paleo-glaciers. Here we use a high-resolution ice sheet model with an accurate representation of grounding line dynamics to study the deglaciation of the marine-based south-western Norwegian sector of the Scandinavian Ice Sheet and its sensitivity to ocean and atmosphere forcing. We find that the regional response to a uniform climate change is highly dependent on the local bedrock topography, consistent with ice sheet reconstructions. Our simulations suggest that ocean warming is able to trigger initial retreat in several fjords, but is not sufficient to explain retreat everywhere. Widespread retreat requires additional ice thinning driven by surface melt. Once retreat is triggered, the underlying bedrock topography and fjord width control the rate and extent of retreat, while multi-millennial changes over the course of deglaciation are modulated by surface melt. We suggest that fjord geometry, ice-ocean interactions and grounding line dynamics are vital controls of decadal-to centennial scale ice sheet mass loss. However, we postulate that atmospheric changes are the most important drivers of widespread ice sheet demise, and will likely trump oceanic influence on future ice sheet mass loss and resulting sea level rise over centennial and longer time scales. publishedVersion

We present a new time-slice reconstruction of the Eurasian ice sheets (British-Irish, Svalbard-Barents-Kara Seas and Scandinavian) documenting the spatial evolution of these interconnected ice sheets every 1000 years from 25 to 10 ka, and at four selected time periods back to 40 ka. The time-slice maps of ice-sheet extent are based on a new Geographical Information System (GIS) database, where we have collected published numerical dates constraining the timing of ice-sheet advance and retreat, and additionally geomorphological and geological evidence contained within the existing literature. We integrate all uncertainty estimates into three ice-margin lines for each time-slice; a most-credible line, derived from our assessment of all available evidence, with bounding maximum and minimum limits allowed by existing data. This approach was motivated by the demands of glaciological, isostatic and climate modelling and to clearly display limitations in knowledge. The timing of advance and retreat were both remarkably spatially variable across the ice-sheet area. According to our compilation the westernmost limit along the British-Irish and Norwegian continental shelf was reached up to 7000 years earlier (at c. 27-26 ka) than the eastern limit on the Russian Plain (at c. 20-19 ka). The Eurasian ice sheet complex as a whole attained its maximum extent (5.5 Mkm2) and volume (~24 m Sea Level Equivalent) at c. 21 ka. Our continental-scale approach highlights instances of conflicting evidence and gaps in the ice-sheet chronology where uncertainties remain large and should be a focus for future research. Largest uncertainties coincide with locations presently below sea level and where contradicting evidence exists. This first version of the database and time-slices (DATED-1) has a census date of 1 January 2013 and both are available to download via the Bjerknes Climate Data Centre and PANGAEA (www.bcdc.no; http://doi.pangaea.de/10.1594/PANGAEA.848117)

We present 18 new cosmogenic ¹⁰Be exposure ages that constrain the breakup time of the Norwegian Channel Ice Stream (NCIS) and the initial retreat of the Scandinavian Ice Sheet from the Southwest coast of Norway following the Last Glacial Maximum (LGM). Seven samples from glacially transported erratics on the island Utsira, located in the path of the NCIS about 400 km up-flow from the LGM ice front position, yielded an average ¹⁰Be age of 22.0 ± 2.0 ka. The distribution of the ages is skewed with the 4 youngest all within the range 20.2–20.8 ka. We place most confidence on this cluster of ages to constrain the timing of ice sheet retreat as we suspect the 3 oldest ages have some inheritance from a previous ice free period. Three additional ages from the adjacent island Karmøy provided an average age of 20.9 ± 0.7 ka, further supporting the new timing of retreat for the NCIS. The ¹⁰Be ages from Utsira and Karmøy suggest that the ice stream broke up about 2000 years earlier than the age assignment based on ¹⁴C ages on foraminifera and molluscs from marine sediment cores. We postulate that the Scandinavian Ice Sheet flowed across the Norwegian Channel to Denmark and onto the North Sea plateau during early phases of the LGM. When the NCIS started to operate this ice supply to the North Sea was cut off and the fast flow of the NCIS also led to a lowering of the ice surface along the Norwegian Channel and thereby drawdown of the entire ice sheet. This facilitated rapid calving of the ice front in the North Sea and we reconstruct a large open bay across the entire northern North Sea by ∼20 ka based on our ¹⁰Be ages in the east and radiocarbon ages from marine cores in the west. Additional ¹⁰Be ages show that the mainland slightly east of the islands Utsira and Karmøy remained ice covered until about 16 ka, indicating almost no net ice-margin retreat for the 4000 years between 20 and 16 ka. After 16 ka the ice margin retreated quickly up-fjord.

We present 34 new cosmogenic 10Be exposure ages that constrain the Lateglacial (Bolling–Preboreal) history of the Scandinavian Ice Sheet in the Lysefjorden region, south-western Norway. We find that the classical Lysefjorden moraines, earlier thought to be entirely of Younger Dryas age, encompass three adjacent moraines attributed to at least two ice sheet advances of distinctly different ages. The 10Be age of the outermost moraine (14.0 ± 0.6 ka; n = 4) suggests that the first advance is of Older Dryas age. The innermost moraine is at least 2000 years younger and was deposited near the end of the Younger Dryas (11.4 ± 0.4 ka; n = 7). After abandonment of the innermost Lysefjorden Moraine, the ice front receded quickly towards the head of the fjord, where recession was interrupted by an advance that deposited the Trollgaren Moraine at 11.3 ± 0.9 ka (n = 5). 10Be ages from the inboard side of the Trollgaren Moraine suggest final retreat by 10.7 ± 0.3 ka (n = 7). The late culmination of the Younger Dryas advance contrasts with other sectors of the Scandinavian Ice Sheet where the margin appears to have culminated earlier during the Younger Dryas stadial, followed by retreat during the middle and late part of the Younger Dryas.

We present geomorphological evidence of large, previously undocumented, early Holocene ice-dammed lakes in the Scandinavian Mountains of northwestern Sweden. The lakes extents indicate that the last remnants of the Scandinavian Ice Sheet were located east of the mountain range. Some early pioneering works have presented similar reconstructions, whereas more recently published reconstructions place the last ice remnants in the high mountains of Sarek. Using high-resolution airborne LiDAR data we have mapped a large number of hitherto undocumented shorelines in some of the main valleys within the northern Scandinavian mountain range. Our results indicate that a larger system of ice-dammed lakes existed in this region than previously thought. The lakes were dammed between the main water divide to the west and the retreating ice sheet margin to the east. The shorelines dip towards the northwest with gradients ranging from 0.5 to 0.4 m/km, from the oldest to the youngest. Further, we have compiled Lateglacial and Holocene shoreline data along the Norwegian coast and from within the Baltic Sea basin and reconstructed the isostatic uplift along a 1400 km long northwest-southeast transect from the Norwegian Sea to Lake Ladoga. By comparing the measured ice-dammed lake shoreline gradients to the dated marine shorelines, we infer that the lakes may have existed for several centuries following 10.2 cal ka BP. We also describe large deposits and extensive erosive features, which demonstrate that a catastrophic glacial lake outburst flood (GLOF) took place eastward along the Pite River Valley. Based on cross-cutting relations to raised shorelines developed in the early Holocene Ancylus Lake (Baltic Sea basin) we conclude that the flood and thus the final phase of deglaciation took place within the time interval 10.3–9.9 cal ka BP. publishedVersion

Kruger, L. C., Paus, A., Svendsen, J. I. & Bjune, A. E. 2011: Lateglacial vegetation and palaeoenvironment in W Norway, with new pollen data from the Sunnmore region. Boreas, 10.1111/j.1502-3885.2011.00213.x. ISSN 0300-9483. Two sediment sequences from Sunnmore, northern W Norway, were pollen-analytically studied to reconstruct the Lateglacial vegetation history and climate. The coastal Dimnamyra was deglaciated around 15.3 ka BP, whereas Lokjingsmyra, further inland, became ice-free around 14 ka BP. The pioneer vegetation dominated by snow-bed communities was gradually replaced by grassland and sparse heath vegetation. A pronounced peak in Poaceae around 12.9 ka BP may reflect warmer and/or drier conditions. The Younger Dryas (YD) cooling phase shows increasing snow-bed vegetation and the local establishment of Artemisia norvegica. A subsequent vegetation closure from grassland to heath signals the Holocene warming. Birch forests were established 500–600 years after the YD–Holocene transition. This development follows the pattern of the Sunnmore region, which is clearly different from the Empetrum dominance in the Lateglacial interstadial further south in W Norway. The Lateglacial oscillations GI-1d (Older Dryas) and GI-1b (Gerzensee) are hardly traceable in the north, in contrast to southern W Norway. The southern vegetation was probably closer to an ecotone and more susceptible to climate changes.

Novaya Zemlya was covered by the eastern part of the Barents–Kara ice sheet during the glacial maximum of marine isotope stage 2 (MIS 2). We obtained 14C ages on 37 samples of mollusc shells from various sites on the islands. Most samples yielded ages in the range of 48–26 14C Ky. Such old samples are sensitive to contamination by young 14C, and therefore their reliability was assessed using replicate analyses and amino acid geochronology. The extent of aspartic acid racemization (Asp D/L) indicates that many of the 14C ages are correct, whereas some are minimum ages only. The results indicate that a substantial part of Novaya Zemlya was ice-free about 35–27 14C Kya, and probably even earlier. Corresponding shorelines up to >140 m a.s.l. indicate a large Barents–Kara ice sheet during early MIS 3. These results are consistent with findings from Svalbard and northern Russia: in both places a large MIS 4/3 Barents–Kara ice sheet is postulated to have retreated about 50 Kya, followed by an ice-free interstadial that lasted until up to ca. 25 Kya. The duration of the MIS 2 glaciation in Novaya Zemlya was calculated by applying the D/L values to a kinetic equation for Asp racemization. This indicates that the islands were ice covered for less than 3000 years if the basal temperature was 0oC, and for less than 10 000 years if it was -5oC.

After the first emergence following deglaciation, relative sea level rose by 10 m in western Norway and culminated late in the Younger Dryas (YD). The relative sea-level history, reconstructed by dating deposits in isolation basins, shows a sea-level low-stand between � 13 640 and 13 080 cal yr BP, a 10 m sea-level rise between � 13 080 and 11 790 cal yr BP and a sea-level high-stand between � 11 790 and 11 550 cal yr BP. Shortly after the YD/Holocene boundary, sea level fell abruptly by � 37 m. The shorelines formed during the sea-level low-stand in the mid-Allerod and during the sea-level high-stand in the YD have almost parallel tilts with a gradient of � 1.3 m km � 1 , indicating that hardly any isostatic movement has taken place during this period of sea-level rise. We conclude that the transgression was caused by the major re-advance of the Scandinavian Ice Sheet that took place in western Norway during the Lateglacial. The extra ice load halted the isostatic uplift and elevated the geoid due to the increased gravitational attraction on the sea. Our results show that the crust responded to the increased load well before the YD (starting � 12 900 cal yr BP), with a sea-level low-stand at 13 640 cal yr BP and the subsequent YD transgression starting at 13 080 cal yr BP. Thus, we conclude that the so-called YD ice-sheet advance in western Norway started during the Allerod, possibly more than 600 years before the Allerod/YD transition. r 2007 Elsevier Ltd. All rights reserved.

Large proglacial lakes cool regional summer climate because of their large heat capacity, and have been shown to modify precipitation through mesoscale atmospheric feedbacks, as in the case of Lake Agassiz(1). Several large ice-dammed lakes, with a combined area twice that of the Caspian Sea, were formed in northern Eurasia about 90,000 years ago, during the last glacial period when an ice sheet centred over the Barents and Kara seas(2) blocked the large northbound Russian rivers(3). Here we present high-resolution simulations with an atmospheric general circulation model that explicitly simulates the surface mass balance of the ice sheet. We show that the main influence of the Eurasian proglacial lakes was a significant reduction of ice sheet melting at the southern margin of the Barents - Kara ice sheet through strong regional summer cooling over large parts of Russia. In our simulations, the summer melt reduction clearly outweighs lake-induced decreases in moisture and hence snowfall, such as has been reported earlier for Lake Agassiz1. We conclude that the summer cooling mechanism from proglacial lakes accelerated ice sheet growth and delayed ice sheet decay in Eurasia and probably also in North America.

Sediment cores from lakes Kormovoye and Oshkoty in the glaciated region of the Pechora Lowland, northern Russia, reveal sediment gravity flow deposits overlain by lacustrine mud and gyttja. The sediments were deposited mainly during melting of buried glacier ice beneath the lakes. In Lake Kormovoye, differential melting of dead ice caused the lake bottom to subside at different places at different times, resulting in sedimentation and erosion occurring only some few metres apart and at shifting locations, as further melting caused inversion of the lake bottom. Basal radiocarbon dates from the two lakes, ranging between 13 and 9 ka, match with basal dates from other lakes in the Pechora Lowland as well as melting of ice-wedges. This indicates that buried glacier ice has survived for ca. 80 000 years from the last glaciation of this area at 90 ka until about 13 ka when a warmer climate caused melting of permafrost and buried glacier ice, forming numerous lakes and a fresh-looking glacial landscape. Copyright 2003 John Wiley & Sons, Ltd.

Glacial landforms in northern Russia, from the Timan Ridge in the west to the east of the Urals, have been mapped by aerial photographs and satellite images supported by field observations. An east-west trending belt of fresh hummock-and-lake glaciokarst landscapes has been traced to the north of 67°N. The southern boundary of these landscapes is called the Markhida Line, which is interpreted as a nearly synchronous limit of the last ice sheet that affected this region. The hummocky landscapes are subdivided into three types according to the stage of postglacial modification: Markhida, Harbei and Halmer. The Halmer landscape on the Uralian piedmont in the east is the freshest, whereas the westernmost Markhida landscape is more eroded. The west- east gradient in morphology is considered to be a result of the time-transgressive melting of stagnant glacier ice and of the underlying permafrost. The pattern of ice-pushed ridges and other directional features reflects a dominant ice flow direction from the Kara Sea shelf. Traces of ice movement from the central Barents Sea are only discernible in the Pechora River left bank area west of 50°E. In the Polar Urals the horseshoe-shaped end moraines at altitudes of up to 560 m a.s.l. reflect ice movement up-valley from the Kara Ice Sheet, indicating the absence of a contemporaneous ice dome in the mountains. The Markhida moraines, superimposed onto the Eemian strata, represent the maximum ice sheet extent in the western part of the Pechora Basin during the Weichselian. The Markhida Line truncates the huge arcs of the Laya-Adzva and Rogovaya ice-pushed ridges protruding to the south. The latter moraines therefore reflect an older ice advance, probably also of Weichselian age. Still farther south, fluvially dissected morainic plateaus without lakes are of pre-Eemian age, because they plunge northwards under marine Eemian sediments. Shorelines of the large ice-dammed Lake Komi, identified between 90 and 110 m a.s.l. in the areas south of the Markhida Line, are radiocarbon dated to be older than 45 ka. The shorelines, incised into the Laya-Adzva moraines, morphologically interfinger with the Markhida moraines, indicating that the last ice advance onto the Russian mainland reached the Markhida Line during the Middle or Early Weichselian, before 45 ka ago.

Late Quaternary sediment yields from the Isfjorden drainage area ($$7327 km^{2}$$), a high arctic region on Svalbard characterized by an alpine landscape, have been reconstructed by using seismic stratigraphy supported by sediment core analysis. The sediments that accumulated in the fjord during and since deglaciation can be divided into three stratigraphic units. The volumes of these units were determined and converted into sediment yield rates averaged over the drainage basin. During deglaciation, 13 to 10 ka, the sediment yield was $$\sim 860 tons(t) \cdot km^{-2} \cdot yr^{-1}$$. In the early Holocene it decreased to $$190 t \cdot km^{-2} \cdot yr^{-1}$$, and then increased to $$390 t \cdot km^{-2} \cdot yr^{-1}$$ during the late Holocene Little Ice Age. When normalized to the approximate glacierized area, these rates correspond to a sediment yield of $$\sim 800 t \cdot km^{-2} \cdot yr^{-1}$$. Sediment yield from non-glacierized parts of the drainage is estimated to be $$35 t \cdot km^{-2} \cdot yr^{...

Contrary to what Zwyns et al . claim on a bibliographical basis, the lithic industry of Byzovaya cannot belong to the Streletskayan complex or be considered as Upper Palaeolithic (UP). Direct analysis of northern assemblages and of Streletskayan technologies reveals incompatible features between these industries. Byzovaya is structured on specific Mousterian technologies and does not show any unique features of the UP.

Palaeolithic sites in Russian high latitudes have been considered as Upper Palaeolithic and thus representing an Arctic expansion of modern humans. Here we show that at Byzovaya, in the western foothills of the Polar Urals, the technological structure of the lithic assemblage makes it directly comparable with Mousterian Middle Palaeolithic industries that so far have been exclusively attributed to the Neandertal populations in Europe. Radiocarbon and optical-stimulated luminescence dates on bones and sand grains indicate that the site was occupied during a short period around 28,500 carbon-14 years before the present (about 31,000 to 34,000 calendar years ago), at the time when only Upper Palaeolithic cultures occupied lower latitudes of Eurasia. Byzovaya may thus represent a late northern refuge for Neandertals, about 1000 km north of earlier known Mousterian sites.

The recent mass loss of the Greenland ice sheet (Chen et al. 2006), the observed increases in the velocity of its fast-flowing outlets (Luthcke et al. 2006) and the melting of the permafrost demonstrate the profound changes occurring in the Arctic region as a result of global warming (ACIA 2005). This is corroborated by systematic satellite monitoring that shows there has been a progressive decrease in the extent of sea ice over the last 30 years, with a record low in 2007 (Comiso et al. 2008). Forward modelling predicts accelerated rates of sea-ice disintegration and the almost complete disappearance of Arctic Ocean summer sea-ice cover within this century. It is clear that the environment in the Arctic is changing at a pace not previously monitored by humankind. It is equally clear, however, that to place the current changes in a millennial time perspective, we need to know more about the Pleistocene natural variability and amplitude of, for example, the Greenland ice sheet, Arctic Ocean sea ice and permafrost. Such a longer time perspective can only be established through international collaborative and multidisciplinary studies of nature’s own archives, such as marine and terrestrial stratigraphic records, sediment distribution and landforms.

Recent studies have shown that northeastern Europe was occupied by humans significantly earlier than previously thought. Some traces of human presence in the European Arctic even date back to about 35-40 ka. This paper discusses the Middle and early Upper Palaeolithic (EUP) assemblages from this area within the local context of their environmental characteristics, as well as their implications for our views on the occupational history of northern environments.

This paper summarizes the results of studies of the Late Weichselian periglacial environments carried out in key areas of northern Eurasia by several QUEEN teams (European Science Foundation (ESF) programme: “Quaternary Environment of the Eurasian North”). The palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the EU funded project “Eurasian Ice Sheets”. These data prove beyond any doubt, that with the exception of the northwestern fringe of the Taymyr Peninsula, the rest of the Eurasian mainland and Severnaya Zemlya were not affected by the Barents–Kara Sea Ice Sheet during the Last Glacial Maximum (LGM). Inversed modelling based on these results shows that a progressive cooling which started around 30 ka BP, caused ice growth in Scandinavia and the northwestern areas of the Barents–Kara Sea shelf, due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets. In the rest of the Eurasian Arctic extremely low precipitation rates (less than 50 mm yr−1), did not allow ice sheet growth in spite of the very cold temperatures. Palaeoclimatic and palaeoenvironmental conditions for the time prior to, during, and after the LGM have been reconstructed for the non-glaciated areas around the LGM ice sheet with the use of faunal and vegetation records, permafrost, eolian sediments, alluvial deposits and other evidences. The changing environment, from interstadial conditions around 30 ka BP to a much colder and drier environment at the culmination of the LGM at 20–15 ka BP, and the beginning of warming around 15 ka BP have been elaborated from the field data, which fits well with the modelling results.

The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (>140 ka), (2) the Early Weichselian (100–80 ka), (3) the Middle Weichselian (60–50 ka) and (4) the Late Weichselian (25–15 ka). The reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic- and sediment core data. The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90–80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60–50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr. A numerical ice-sheet model, forced by global sea level and solar changes, was run through the full Weichselian glacial cycle. The modeling results are roughly compatible with the geological record of ice growth, but the model underpredicts the glaciations in the Eurasian Arctic during the Early and Middle Weichselian. One reason for this is that the climate in the Eurasian Arctic was not as dry then as during the Late Weichselian glacial maximum.

Lake and peat deposits from the Timan Ridge, Arctic Russia, were pollen analysed, reconstructing the vegetation history and paleoenvironment since the Last Glacial Maximum (LGM) 20–18,000 years ago. The sites studied are located inside the margins of a large paleolake of about 20 km 2 , by us named Lake Timan. This lake developed in the Late Weichselian, more than 30,000 years after the deglaciation of this region, and was formed due to increased precipitation and warmer summers that accelerated the melting of stagnant ice within its catchment. The lake was drained during the early Holocene when the outlet rivers eroded the spillways. A new generation of much smaller lakes formed during the Holocene when the last remnants of buried glacier ice melted away causing the exposed floor of Lake Timan to subside. Since deglaciation, the following regional vegetation development has been recorded: (1) During the initial stage of Lake Timan, the dominant vegetation was discontinuous steppe/tundra, with patches of snow bed vegetation. (2) A dwarf-shrub tundra established during the Late Weichselian interstadial (Allerod), probably reflecting warmer and moister conditions. (3) The Younger Dryas cooling is recognised by a reversal to steppe/tundra and snowbeds on unstable mineral-soils, and higher palynological richness. (4) Soon after the transition into the Holocene, a birch-forest established on the Timan Ridge. (5) A cooling starting around 8200 cal. years BP initiated the deforestation of the exposed hills. In the most protected sites, birch trees persisted until later than 4000 years ago, reflecting a gradual development into the present treeless dwarf-shrub tundra.

The transition from the Middle to the Upper Palaeolithic, approximately 40,000-35,000 radiocarbon years ago, marks a turning point in the history of human evolution in Europe. Many changes in the archaeological and fossil record at this time have been associated with the appearance of anatomically modern humans. Before this transition, the Neanderthals roamed the continent, but their remains have not been found in the northernmost part of Eurasia. It is generally believed that this vast region was not colonized by humans until the final stage of the last Ice Age some 13,000-14,000 years ago. Here we report the discovery of traces of human occupation nearly 40,000 years old at Mamontovaya Kurya, a Palaeolithic site situated in the European part of the Russian Arctic. At this site we have uncovered stone artefacts, animal bones and a mammoth tusk with human-made marks from strata covered by thick Quaternary deposits. This is the oldest documented evidence for human presence at this high latitude; it implies that either the Neanderthals expanded much further north than previously thought or that modern humans were present in the Arctic only a few thousand years after their first appearance in Europe.

The history of the Late Weichselian northwestern Barents Shelf, including western Svalbard, has been investigated by provenance/sedimentologist studies of five cores from the continental shelf and slope west of Svalbard. The chronostratigraphy of the cores is based on AMS 14C dates and oxygen isotope analyses. Interpretations of the cores suggest that the ice sheets of western Svalbard and northwestern Barents Sea experienced advances and retreats in two steps. The first significant ice advance beyond the present coastline occurred ca. 22,000 14C yr B.P. and was followed by an ice advance to the shelf edge ca. 18,000 14C yr B.P. Ice recession from the outer shelf and the southwestern Barents Sea began 14,800 14C yr B.P. and was followed by a second ice recession between 13,000 and 12,000 14 C yr B.P. during which ice withdrew from the inner shelf. A minor readvance of the ice sheet on the shelf west of Svalbard occurred close to 12,400 14C yr B.P. The first deglaciation event was associated with release of icebergs containing ice-rafted detritus, while the later episode also included significant amounts of meltwater and fine-grained sediment.

(1) Calculation of the sea level high latitude production rate based on the samples from the Herdla-Halsnoy Younger Dryas end moraine required accounting for the isostatic rebound of the site following deglaciation (Lohne et al., 2007). In the process of calculating exposure ages of samples from nearby sites, it was realized that the original calibration of the production rates from Halsnoy were calculated using a correction based on the relative sea level history (70m maximum) plus the eustatic sea level history (50m at maximum), i.e. that the amount of isostatic depression had been over corrected. Sea level high latitude Be production rates based on the correct relative sea level history are presented below in a corrected version of Table 2. (2) In the original publication, the ‘Combined’ production rates were determined using a chi-squared minimization based on the data from both calibration sites. However, because the two studied sites have significantly different ages (Halsnoy 11650 100 and Oldedalen 6070 111), and therefore integrate production over different lengths of time, it is inappropriate to determine a sea level high latitude production rate for the entire data set, using the chi-squared minimization. Instead, the arithmetic mean of the production rates from the two sites is the more appropriate average production rate. We present in the corrected Table 2 below both the updated production rate values for the samples from Halsnoy and average production rates using the arithmetic mean and standard deviation of the production rates from the two sites. We apologize for any inconvenience caused. References

Lake Linnévatnet is situated near the mouth of Isfjorden, on thc west coast of Spitsbergen (Fig. 1A). According to Denton & Hughes (1981) and Mangerud et al. (1987) it lies within the Late Weichselian ice boundary. whereas according to Boulton (1979) and Troitsky et al. (1979) it is outside that boundary. The purpose of this paper is to describe the stratigraphy of the lake sediments and discuss the timing of the glacial retreat.