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Distinct Younger Dryas (YD) moraines are mapped more-or-less continuously around the Scandinavian Ice Sheet. In most areas there is no evidence to suggest that a glacial re-advance took place during the YD, either because it did not happen or because older deposits have been removed by glacial erosion. In contrast we here present 90 radiocarbon dates from 36 different sites that were overrun by a major ice sheet advance in the area between Hardangerfjorden and Sognefjorden, SW Norway. Thus this region is exceptional for examining the glacial response to the climate shifts across Allerod-YD. The re-growth of the ice sheet in this sector commenced during the Allerod Interstadial. It expanded along 600–800 m deep fjords reaching a thickness of up to 2000 m. We produce time–distance diagrams for two lobes; for both the outermost coast became ice free close to 15 cal ka BP, i.e. at the onset of the Bolling. The Hardangerfjorden Lobe re-advanced during the Older Dryas (14 cal ka BP), an event that was not replicated for the Herdla Lobe farther north. Both lobes reached their most landward position before re-advancing at 13.5–13.0 cal ka and obtained their maximum extent at the very end of the YD, 11.5 cal ka. The late culmination of the advance is accurately dated and differs from most of the Scandinavian Ice Sheet margin where the maximum was reached during early or middle YD. We also present a time–distance diagram from the Last Glacial Maximum to the ice divide showing two-step retreat; fast retreat occurs 21–20 and 11.5–10 cal ka BP separated by a period of almost no net retreat 20–11.5 cal ka BP, which contrasts with much more even retreat in other parts of the Scandinavian Ice Sheet.

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 describe and discuss the glacial and climate variations in the Polar Ural Mountains in northern Russia over the last 100 000 years. A series of optically stimulated luminescence (OSL) and radiocarbon ages from sediment cores demonstrate that there has been continuous deposition of lacustrine sediments throughout the last 65 ka in Lake Gerdizty, a lake basin situated on the eastern foothills of the Urals. Below the lacustrine sequence are two till beds; the uppermost (unit B) was probably deposited by a large mountain-centred glacier complex that covered the lake basin during Marine Isotope Stage (MIS) 4. This till bed might be a counterpart of the Usa Moraine in the western foothills of the Polar Urals, which is dated with OSL- and 10 Be cosmogenic nuclide methods to between 68 and 58 ka, consistent with the OSL ages from the lowermost lacustrine sediments in Lake Gerdizty. During this glaciation some of the northern Uralian outlet glaciers probably merged with the adjacent Barents–Kara Ice Sheet that reached onto the adjacent lowlands forming large ice-dammed lakes on both sides of the Ural Mountains. The equilibrium line altitude (ELA) on the local ice cap was then at least 1200 m lower than at present. The pollen stratigraphy in Lake Gerditzy reflects an open tundra and steppe-like vegetation throughout MIS 3–2 (60–11,7 ka). The first significant change in vegetation, shown by an increase of dwarf-shrub communities of Salix and Betula , took place during the Lateglacial at around 15 ka or shortly after. Birch and spruce trees approached the area for the first time soon after the Holocene transition ∼11.7 ka, and became dominant elements in the vegetation after a few hundred years. Our reconstruction suggests a very cold summer climate during MIS 4 and presumably also during the preceding MIS 5b (95–85 ka) glaciation, probably amplified by the large ice-dammed lakes that existed during these two glaciations. A somewhat milder climate prevailed during MIS 3 (60–25 ka), but a treeless vegetation nevertheless suggests that mean summer temperatures did not exceed 10–12 °C before the earliest Holocene.

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

We present a reconstruction of the timing and retreat rates of more than 2000 m thick Younger Dryas (YD) fjord glaciers in western Norway using a detailed chronology of 10 Be exposure ages from lateral moraines and 14 C dated end moraines. A primary conclusion is that ice margins retreated up the 120–170 km long fjords at mean rates of 240–340 m yr −1 during the early Holocene. We further show that part of the south-western sector of the Scandinavian Ice Sheet collapsed in two distinct steps. The first step occurred between 19.5 and 18.5 ka BP as break up of the Norwegian Channel Ice Stream, which drained the ice sheet during the Last Glacial Maximum (LGM). The second step was the rapid retreat up the fjords mentioned above, dated to 11.6–11.1 ka BP. During the intervening ∼7000 years no net retreat occurred despite oscillations of the ice margin. This stepwise ice margin retreat strongly contrasts with the more monotonic decay of the ice sheet as a whole, indicating that water depths set the pace for climate-triggered ice margin retreat in this part of the ice sheet. Calving and melting of marine margins has dominated mass-loss from modern ice sheets in recent decades; however, the mechanisms and long-term (100–1000 yr) rate of ice-front retreat is less certain and empirical examples such as those given here may help in developing better numerical models.

We review geo-archaeological results from six Palaeolithic sites along the western flank of the northern Ural Mountains. The oldest traces of human activities, dated to around 36–35 14C ka BP (43–40 cal ka), were found in alluvial strata at Mamontovaya Kurya at the Polar Circle - their connection to cultures further south remains uncertain. Slightly younger artefacts were found at the site Zaozer’e, nearly a thousand km further to the south, where a rich archaeological assemblage, dated to 34–33 14C ka BP (39–37 cal ka), was uncovered from underneath several meters of loess. The assemblage contains some small “Middle Palaeolithic like” bifaces alongside distinct Upper Palaeolithic traits, such as well-defined blades. This site also contains some perforated “pendants” made of freshwater molluscs. At the Byzovaya site, located at 65°N and radiocarbon dated to about 30–29 14C ka BP (34–32 cal ka), more than 300 artefacts and several thousand animal remains, mostly of mammoth, were incorporated in coarse-grained debris-flow deposits, sealed by aeolian sand. Pending the results from a new technological analysis of the whole artefact assemblage we can yet not decide whether Byzovaya should be categorized as a Middle- or Upper Palaeolithic site. The finds from Garchi, located in a loess sequence near Zaozer’e, have a similar or slightly younger age than the material from Byzovaya. Also at this site bifacial tools are present; alongside some characteristic triangle projectile points as well as some other elements which have nearly identical counterparts in the Upper Palaeolithic Kostenki/Streletskaya and Sungirian complexes, unambiguously associated with Modern humans. We conclude that the initial human colonisations along the Ural Mountains took place during a relatively favourable period of Marine Isotope Stage 3, when only small mountain glaciers existed in this region. The finds from the Medvezhia Peshera rock shelter have a completely different age (19–16 14C ka BP, 23–19 cal ka) and character, indicating that humans also were present along the Urals close to the Last Glacial Maximum (26–19 ka BP), the coldest and driest period of the last ice age. The few artefacts that were uncovered at Pymva Shor, the northernmost site investigated by us, are probably a little younger than those at Medveshia Peshera, but the timing of human presence is not precisely constrained at this site. In view of the obtained results it appears that humans were at least temporarily present in these northern landscapes from more than 40,000 years ago and onwards.

A new volcanic ash, named the Dimna Ash, geochemically similar to the rhyolitic component of the Vedde Ash, is described in a core from a palaeo-lake in Western Norway. The Dimna Ash occurs more than a metre below the Vedde Ash and radiocarbon datings indicate a minimum age of 15,100 calendar years BP (12,800 14 C years BP). In comparison the age of the Vedde Ash is 12,120 calendar (NGRIP) years BP (10,300 14 C years BP). The Dimna Ash is invisible to the naked eye in the core and was detected by applying a density separation technique. It comprises, however, up to 12,900 ash shards per cm 3 sediment. We conclude that the Dimna Ash is wind-blown from Iceland and should therefore be found also in marine cores between Iceland and Norway and thus has the potential to become an important marker horizon. The core also contains scattered ash shards, geochemically similar to the Borrobol Ash, that are spread over a 50 cm thick zone deposited between 13,400 and 12,700 calendar years BP. This is the first discovery of Borrobol-like ash in Norway.

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.

It has been a long-standing discussion whether the Barents–Kara Ice Sheet expanded onto mainland Russia during the Last Glacial Maximum (LGM). In this paper, we describe many well-dated (by conventional and AMS 14 C methods and optically stimulated luminescence) sedimentary sequences in the controversial area of Northern Russia. The sequences discussed are not covered by till, and yet all predate the LGM. The deposits consist mostly of aeolian or lacustrine, easily deformable soft silt and fine sand. Two sites feature frozen mammoth carcasses and three sites contain Palaeolithic artefacts and mammalian bones. We emphasise that these formations show no sign of having been overridden by an ice sheet. At several sites, deposition of aeolian sediments and formation of ice wedges took place during the LGM time span. These observations present unambiguous proof that the Barents–Kara Ice Sheet did not cover mainland Russia during LGM, with a possible exception for the northern tip of the Taimyr Peninsula. r 2001 Elsevier Science Ltd. All rights reserved.

The timing, extent and configuration of the Late Weichselian Barents ice sheet has been debated for several decades. This debate has arisen largely because of the limited or conflicting field evidence on which most models have been based. In particular, reconstruction of the marine parts of the former Barents ice sheet has been controversial. This paper aims to review the geological observations and interpretations regarding the size and timing of the Late Weichselian ice sheet, combined with numerical modelling of its formation in order to produce a reconstruction of ice sheet extent and behaviour. Sub-glacial till with overlying glacimarine deposits dated to the Late Weichselian is found over most of the Barents Sea floor and the continental shelf west of Svalbard. Glacially induced debris flow deposits on the large Bjonoya and Isfjorden trough mouth fans strongly support the idea of ice sheet extension to the shelf edge during maximum glaciation. Isobase maps show a centre of post-glacial uplift in the north-central Barents Sea, and glaciological and isostatic modelling suggest that the ice sheet was 2000–3000 m thick in this area. The ice sheet was confluent with ice over the Kara Sea, but the interaction between the Barents and Kara ice sheets is not yet fully understood. The deglaciation of the Barents ice sheet started ca 15 ka, probably by calving within the deeper troughs. By 12 ka, most of the central Barents Sea was ice free, and ice remained over the Svalbard, Franz Josef Land and Novaja Zemlya archipelagos and adjacent shallow shelf areas. The coasts and fjords of these islands were ice free by 10 ka.

On Spitsbergen, western Svalbard, three major glacial advances have been identified during the Weichselian. All three reached the continental shelf west of the Svalbard archipelago. Radiocarbon, luminescence and amino acid dating of interbedded interstadial and interglacial sediments indicate that these glacial advances have Early (Isotope Stage 5d), Middle (Stage 4), and Late Weichselian ages (Stage 2). An additional, more local, advance has been dated to Isotope Stage 5b. The Late Weichselian ice sheet expanded across the entire Barents Sea. However, in the south-western Barents Sea, the Late Weichselian till is the only till above Eemian sediments, indicating that the Early- and Middle Weichselian ice advances were restricted to the Svalbard archipelago and the northern Barents Sea. A major problem with the onshore sites is the dating of events beyond the range of the radiocarbon method. To overcome this, the onshore record has been correlated with marine cores from the continental slope and the deep-sea west of Svalbard, where a chronology has been established by oxygen isotope stratigraphy. Ice rafted detritus (IRD) was used as the main monitor of glaciation. The IRD record closely mirrors the glaciation history as interpreted from the onshore sections. During the Late Weichselian, the largest IRD peak occurred during deglaciation, a pattern also postulated for the earlier events. Given this, the results from the marine cores indicate that the ages for the first glacial advances during the Weichselian were a few thousand years older than interpreted from the onshore stratigraphy.

The glaciation history of Svalbard (78°N) and the NW Barents Sea is reconstructed for the last 130 ka, based on studies of sediments exposed in coastal cliffs at the head of Isfjorden. Four different till beds separated by marine sediments are recognized. The lowest marine formation, containing Mytilus edulis, reflects warmer conditions than at present, and is correlated with the last interglacial, the Eemian of Europe and Oxygen Isotope Substage 5e in the deep sea. The post-Eemian tills are inferred to represent major glaciations around 110 ka BP, 75-50 ka BP, and 25-10 ka BP. During the intervening intervals the glaciers on Svalbard were not significantly larger than at present and the NW Barents Sea was probably ice-free. The ice-free periods, named Phantomodden and Kapp Ekholm interstadials, lasted from about 110 to 75 and from 50 to 25 ka BP respectively. The marine fauna from both these interstadials indicate seasonally ice free conditions. The ages of the recorded glaciations coincide with, or are slightly younger than, periods with insolation minima, which at this latitude is determined by a low tilt of the Earth's axis. Thus we postulate that the Quaternary glaciations of Svalbard were driven by orbital variations with the 41 ka tilt period, in contrast to the lower-latitude glaciations of Scandinavia that were partly driven by the precession cycle with a periodicity of around 23 ka.