Astrid Lyså

A 10,000-Year Record of Arctic Ocean Sea-Ice Variability-View from the Beach

Sea-ice coverage near northern Greenland and in the western Arctic Ocean varied in opposition over much of the Holocene. We present a sea-ice record from northern Greenland covering the past 10,000 years. Multiyear sea ice reached a minimum between ~8500 and 6000 years ago, when the limit of year-round sea ice at the coast of Greenland was located ~1000 kilometers to the north of its present position. The subsequent increase in multiyear sea ice culminated during the past 2500 years and is linked to an increase in ice export from the western Arctic and higher variability of ice-drift routes. When the ice was at its minimum in northern Greenland, it greatly increased at Ellesmere Island to the west. The lack of uniformity in past sea-ice changes, which is probably related to large-scale atmospheric anomalies such as the Arctic Oscillation, is not well reproduced in models. This needs to be further explored, as it is likely to have an impact on predictions of future sea-ice distribution.

Late Pleistocene glacial and lake history of northwestern Russia

Five regionally significant Weichselian glacial events, each separated by terrestrial and marine interstadial conditions, are described from northwestern Russia. The first glacial event took place in the Early Weichselian. An ice sheet centred in the Kara Sea area dammed up a large lake in the Pechora lowland. Water was discharged across a threshold on the Timan Ridge and via an ice-free corridor between the Scandinavian Ice Sheet and the Kara Sea Ice Sheet to the west and north into the Barents Sea. The next glaciation occurred around 75–70 kyr BP after an interstadial episode that lasted c. 15 kyr. A local ice cap developed over the Timan Ridge at the transition to the Middle Weichselian. Shortly after deglaciation of the Timan ice cap, an ice sheet centred in the Barents Sea reached the area. The configuration of this ice sheet suggests that it was confluent with the Scandinavian Ice Sheet. Consequently, around 70–65 kyr BP a huge ice-dammed lake formed in the White Sea basin (the ‘White Sea Lake’), only now the outlet across the Timan Ridge discharged water eastward into the Pechora area. The Barents Sea Ice Sheet likely suffered marine down-draw that led to its rapid collapse. The White Sea Lake drained into the Barents Sea, and marine inundation and interstadial conditions followed between 65 and 55 kyr BP. The glaciation that followed was centred in the Kara Sea area around 55–45 kyr BP. Northward directed fluvial runoff in the Arkhangelsk region indicates that the Kara Sea Ice Sheet was independent of the Scandinavian Ice Sheet and that the Barents Sea remained ice free. This glaciation was succeeded by a c. 20-kyr-long ice-free and periglacial period before the Scandinavian Ice Sheet invaded from the west, and joined with the Barents Sea Ice Sheet in the northernmost areas of northwestern Russia. The study area seems to be the only region that was invaded by all three ice sheets during the Weichselian. A general increase in ice-sheet size and the westwards migrating ice-sheet dominance with time was reversed in Middle Weichselian time to an easterly dominated ice-sheet configuration. This sequence of events resulted in a complex lake history with spillways being re-used and ice-dammed lakes appearing at different places along the ice margins at different times.

Early and Middle Valdaian glaciations, ice-dammed lakes and periglacial interstadials in northwest Russia: new evidence from the Pyoza River area

The Pyoza River area in the Arkhangelsk district exposes sedimentary sequences suitable for study of the interaction between consecutive Valdaian ice sheets in Northern Russia. Lithostratigraphic investigations combined with luminescence dating have revealed new evidence on the Late Pleistocene history of the area. Overlying glacigenic deposits of the Moscowian (Saalian) glaciation marine deposits previously confined to three separate transgression phases have all been connected to the Mikulinian (Eemian) interglacial. Early Valdaian (E. Weichselian) proglacial, lacustrine and fluvial deposits indicate glaciation to the east or north and consequently glacier damming and meltwater run-off in the Pyoza area around 90–110 ka BP. Interstadial conditions with forest-steppe tundra vegetation and lacustrine and fluvial deposition prevailed at the end of the Early Valdaian around 75–95 ka BP. A terrestrial-based glaciation from easterly uplands reached the Pyoza area at the Early to Middle Valdaian transition around 65–75 ka BP and deposited glaciofluvial strata and subglacial till (Yolkino Till). During deglaciation, laterally extensive glaciolacustrine sediments were deposited in ice-dammed lakes in the early Middle Valdaian around 55–75 ka BP. The Barents–Kara Sea ice sheet deposited the Viryuga Till on the lower Pyoza from northerly directions. The ice sheet formed the Pyoza marginal moraines, which can be correlated with the Markhida moraines further east, and proglacial lacustrine deposition persisted in the area during the first part of the Middle Valdaian. Glacio-isostatic uplift caused erosion followed by pedogenesis and the formation of a deflation horizon in the Middle Valdaian. Widely dispersed periglacial river plains were formed during the Late Valdaian around 10–20 ka BP. Thus, the evidence of a terrestrial-based ice sheet from easterly uplands in the Pyoza area suggests that local piedmont glaciers situated in highlands such as the Timan Ridge or the Urals could have developed into larger, regionally confined ice sheets. Two phases of ice damming and development of proglacial lakes occurred during the Early and Middle Valdaian. The region did not experience glaciation during the Late Valdaian.

Late Pleistocene stratigraphy and sedimentary environment of the Arkhangelsk area, northwest Russia

The Arkhangelsk area lies in the region that was reached by the northeastern flank of the Scandinavian ice sheet during the last glaciation. Investigations of Late Pleistocene sediments show interglacial terrestrial and marine conditions with sea level up to 52 m above the present level. An unconformity in the stratigraphy suggests a hiatus representing the Early Valdaian (Weichselian) and the beginning of the Middle Valdaian. This unconformity could be related to a low base level and isostatic depression of the area north of Arkhangelsk, either caused by ice masses advancing from the Kara and Barents ice sheets and/or to Scandinavian ice over the Kola Peninsula. During Middle Valdaian, from c. 66 ka BP, until the advance of the Late Valdaian glacier, c. 17–16 ka BP, peat formation, and northward fluvial sedimentation occurred coexisting with permafrost conditions in a later phase. Before the glacier advance, the base level rose and thick vertical accumulations of fluvial sediments were formed. Associated with this glacier advance from the north–northwest, ice damming occurred. Fluvial drainage was opposite to the present drainage pattern and deposition appeared in glaciolacustrine ponds in the area outside the limit of the glaciation. After the deglaciation that started c. 15 ka BP, permafrost conditions and downwasting of buried stagnant glacier ice prevailed until at least 10.7 ka BP.

Valdaian glacial maxima in the Arkhangelsk district of northwestern Russia

Abstract The marginal configurations and ages of the Valdaian (Weichselian) glacial maxima in northern Russia have hitherto not been well established, thus, numerous versions of the Last Glacial Maximum (LGM) positions of the Scandinavian Ice Sheet are known ( Fig. 1B ). New data on ice sheet growth and decay indicate at least three glacial maxima during the Late Pleistocene each with individual spreading centres and different ages. Results of modern investigations in the Arkhangelsk region, conducted by the authors, are compared with an analysis of previous data on the Late Quaternary geology of Northwest Russia, which comprises a thorough presentation of Russian literature on this subject. This has allowed us to question and revise former models on Valdaian glaciation history and ice-marginal positions in a major part of the Russian North. An Early-Middle Valdaian (c. 70 ka BP) glaciation from the east and southeast, possibly originating on the Timan ridge, crossed the Pyoza River basin and reached the White Sea coast along the Bay of Mezen. The southern terminus of the ice sheet is probably found along parts of the Mezen River ( Fig. 2A,B ). The presence of an Early-Middle Valdaian Scandinavian glaciation, which covered the Arkhangelsk region and in neighbouring areas of Karelia and Vologda is not supported by geological data. In the Middle Valdaian (c. 70 ka BP) an ice sheet from the Barents-Kara Sea flowed from the north, northeast and reached the lower Pyoza River and the south and western shores of Mezen Bay on the White Sea coast. The terminal formations of its maximal stage stretch from west to east just north of Pyoza River and then run marginal to the Timan ridge from the north joining with the Markhida end-moraines on the Pechora Lowland ( Fig. 2A, B ). During the Late Valdaian, the Scandinavian Ice Sheet occupied the northwestern part of the Arkhangelsk region around 19-17 ka BP. The limit of this Late Valdaian glacial maximum runs from the White Sea shore of the Kanin Peninsula in the north, along the Kuloi River south of Mezen to the Middle Pinega River, crossing the rivers Severnaya Dvina and Vaga near the villages of Cherevkovo and Ust-Padenga. The glacial boundary bordered the Melovian and Nyandoma high ground and continued southwestwards to Lake Kubenskoe in the Vologda region. The Pyoza, Mezen and Vashka river basins remained ice-free during the Late Valdaian time, this area being covered by fluvial flood plains, with abundant evidence of permafrost and lakes. The latter have yielded pollen evidence indicating an arctic to subarctic environment between 18-10 ka BP ( Fig. 2A, B ).

Distribution of ice marginal moraines in NW Russia

Here we present results from a mapping project on the distribution of glacial end moraine zones in NW Russia, covering an area from the Baltics in the west (30°E) to Taymyr Peninsula and Byrranga mountains (120°E) in the East. Several previous studies have been made in the area, but none have mapped end moraine zones in a uniform way over the whole field area. We suggest that our mapping of moraine distribution in NW Russia, covering an area of about 7 million km2 is the most consistent to date. Much of the mapped area lies north of 60°N and is thus outside coverage of the high-quality Shuttle Radar Topography Mission digital elevation model. We have been using a new digital elevation data-set consisting of digitized Russian topographic maps (scales 1:100,000 and 1:200,000), combined with optical remote sensing data to map moraine zone distribution. The mapped moraines in this study are largely in agreement with recent reconstructions of former ice sheet extent in the area. However, several previously undocumented moraines have been identified and our results show that the last glacial maximum Scandinavian ice sheet probably extended further east into Russia than previously thought. In other areas, we also add considerable more detail on former ice sheet extent.

Cyclic changes in the sedimentary environment during the last interglacial/glacial cycle; coastal Jameson Land, East Greenland

Abstract Raised successions of sediments from the last interglacial/glacial period along coastal Jameson Land, East Greenland, comprise a variety of sedimentary facies that reflect cyclic changes of the sedimentary environment. These changes are controlled by the fluctuations of relative sea-level and glacier advances. Each of the sedimentary cycles starts with till deposition succeeded by marine mud sedimentation, subaerial erosion, deltaic and coastal sedimentation. Sea-level changes alters from falling to rising during each sedimentary cycle and indicates that local East Greenland glacier fluctuations generally lead the global eustatic cycles. Most of the deposits cover isotope stage 5, and successive higher sea-level stands during each sedimentary cycle indicate a net growth of the Greenland ice sheet during the Early Weichselian.

Ice-Contact Deposits in Fjords From Northern Norway

During the retreat of the Fennoscandian Ice Sheet several ice-contact systems were deposited on the shelf and in the fjords along the norwegian coast (Fig. 1). The most conspicuous system was formed by the glacial readvance during the Younger Dryas chron (10,000–11,000 BP). This system is termed the Tromso-Lyngen moraine in northern Norway [Andersen 1968]. A less distinctive ice-contact system which often is found a few kilometres ice-distal of the Tromso-Lyngen moraine, the Skarpnes moraine, is dated to 12,500–12,000 BP [Andersen 1968, Vorren & Elvsborg 1979]. The submarine parts of these moraines have been mapped by seismic investigations in fjords and sounds [Vorren et al. 1988] and detailed investigation on emerged outcrop data from the Tromso-Lyngen moraine has been done by Lonne [1993].