Late Quaternary glacier and sea-ice history of northern Wijdefjorden,Svalbard

The deglaciation history and Holocene environmental evolution of northern Wijdefjorden, Svalbard, are reconstructed using sediment cores and acoustic data (multibeam swath bathymetry and sub-bottom profiler data). Results reveal that the fjord mouth was deglaciated prior to 14.5±0.3 cal. ka BP and deglaciation occurred stepwise. Biomarker analyses show rapid variations in water temperature and sea ice cover during the deglaciation, and cold conditions during the Younger Dryas, followed by minimum sea ice cover throughout the Early Holocene, until c. 7 cal. ka BP. Most of the glaciers in Wijdefjorden had retreated onto land by c. 7.6±0.2 cal. ka BP. Subsequently, the sea-ice extent increased and remained high throughout the last part of the Holocene. We interpret a high Late Holocene sediment accumulation rate in the northernmost core to reflect increased sediment flux to the site from the outlet of the adjacent lake Femmilsjøen, related to glacier growth in the Femmilsjøen catchment area. Furthermore, increased sea ice cover, lower water temperatures and the re-occurrence of ice-rafted debris indicate increased local glacier activity and overall cooler conditions in Wijdefjorden after c. 0.5 cal. ka BP. We summarize our findings in a conceptual model for the depositional environment in northern Wijdefjorden from the Late Weichselian until present.     

Wahlenbergfjord,eastern Svalbard: a glacier‐surrounded fjord reflecting regional hydrographic variability during the Holocene?

Exceptionally high sedimentation rates in Arctic fjords provide the possibility to reconstruct environmental conditions in high temporal resolution during the (pre‐)Holocene. The unique geographical location of Svalbard at the intersection of Arctic and Atlantic waters offers the opportunity to estimate local (mainly glacier‐related) vs. regional (hydrographic) variabilities. Sedimentological, micropalaeontological and geochemical data from the very remote, glacier‐surrounded Wahlenbergfjord in eastern Svalbard provides information on glacier dynamics, palaeoceanographic and sea‐ice conditions during the Holocene. The present study illustrates a high meltwater discharge during the summer insolation maximum (c. 11.3–7.7 ka) when the intrusion of upwelled relatively warm Atlantic‐derived waters led to an almost open fjord situation with reduced sea ice in summer. Around 7.7 ka, a rapid hydrographic shift occurred: the dominance of inflowing Atlantic‐derived waters was replaced by a stronger influence of Arctic Water reflecting regional palaeoceanographic conditions evident in the benthic foraminiferal fauna also at Svalbard's margins. Neoglacial conditions characterized the late Holocene (c. 3.1–0.2 ka), when glaciers probably advanced as cold atmospheric temperatures were decoupled from the advection of relatively warm intermediate waters probably caused by an extending sea‐ice coverage. Accordingly, our data show that even a remote, glacier‐proximal study site reflects rapid as well as longer‐term regional changes.     

Deglaciation and ice shelf development at the northeast margin of the Laurentide Ice Sheet during the Younger Dryas chronozone

Core 2011804‐0010 from easternmost Lancaster Sound provides important insights into deglacial timing and style at the marine margin of the NE Laurentide Ice Sheet (LIS). Spanning 13.2–11.0 cal. ka BP and investigated for ice‐rafted debris (IRD), foraminifera, biogenic silica and total organic carbon, the stratigraphy comprises a lithofacies progression from proximal grounding line and sub‐ice shelf environments to open glaciomarine deposition; a sequence similar to deposits from Antarctic ice shelves. These results are the first marine evidence of a former ice shelf in the eastern Northwest Passage and are consistent with a preceding phase of ice streaming in eastern Lancaster Sound. Initial glacial float‐off and retreat occurred >13.2 cal. ka BP, followed by formation of an extensive deglacial ice shelf during the Younger Dryas, which acted to stabilize the retreating margin of the NE LIS until 12.5 cal. ka BP. IRD analyses of sub‐ice shelf facies indicate initial high input from source areas on northern Baffin Island delivered to Lancaster Sound by a tributary ice stream in Admiralty Inlet. After ice shelf break‐up, Bylot Island became the dominant source area. Foraminifera are dominated by characteristic ice‐proximal glaciomarine benthics (Cassidulina reniforme, Elphidium excavatum f. clavata), complemented by advected Atlantic water (Cassidulina neoteretis, Neogloboquadrina pachyderma) and enhanced current indicators (Lobatula lobatula). The biostratigraphy further supports the ice shelf model, with advection of sparse faunas beneath the ice shelf, followed by increased productivity under open water glaciomarine conditions. The absence of Holocene sediments in the core suggests that the uppermost deposits were removed, most likely due to mass transport resulting from the site's proximity to modern tidewater glacier margins. Collectively, this study presents important new constraints on the deglacial behaviour of the NE Laurentide Ice Sheet, with implications for past ice sheet stability, ice‐rafted sediment delivery, and ice−ocean interactions in this complex archipelago setting.     

Glacial and climate history of the last 24 000 years in the Polar Ural Mountains,Arctic Russia,inferred from partly varved lake sediments

We present a well‐dated, high‐resolution and continuous sediment record spanning the last c. 24 000 years from lake Bolshoye Shchuchye located in the Polar Ural Mountains, Arctic Russia. This is the first continuous sediment succession reaching back into the Last Glacial Maximum (LGM) ever retrieved from this region. We reconstruct the glacial and climate history in the area since the LGM based on sedimentological and geochemical analysis of a 24‐m‐long sediment core. A robust chronology was established using a combination of AMS ¹⁴C‐dating, the position of the Vedde Ash and varve counting. The varved part of the sediment core spans across the LGM from 24 to 18.7 cal. ka BP. We conclude that the lake basin remained ice‐free throughout the LGM, but that mountain glaciers were present in the lake catchment. A decrease in both glacial varve preservation and sedimentation rate suggests that these glaciers started to retreat c. 18.7 cal. ka BP and had disappeared from the catchment by 14.35 cal. ka BP. There are no indications of glacier regrowth during the Younger Dryas. We infer a distinct climatic amelioration following the onset of the Holocene and an Early to Middle Holocene thermal optimum between 10–5 cal. ka BP. Our results provide a long‐awaited continuous and high‐resolution record of past climate that supplements the existing, more fragmentary data from moraines and exposed strata along river banks and coastal cliffs around the Russian Arctic.     

An 11 000‐year record of driftwood delivery to the western Queen Elizabeth Islands,Arctic Canada

Fifty‐six new radiocarbon dates from driftwood (mainly Larix, Picea and Populus spp.) collected from the modern and raised shorelines of Melville and Eglinton islands (western Canadian High Arctic) are presented and compared to other driftwood collections from the Canadian Arctic Archipelago (CAA) and Greenland. By documenting the species (provenance) and spatio‐temporal distribution of driftwood at various sites across the Arctic, regional characterizations of former sea‐ice conditions and changes in Arctic Ocean circulation patterns may be deduced. The earliest postglacial invasion of the Canadian Arctic Archipelago by driftwood is recorded on central Melville Island at c. 11 cal. ka BP, suggesting that the modern circulation pattern of Arctic Ocean surface water southeast through the archipelago was established >1000 years earlier than previously proposed. Throughout most of the Holocene until c. 1.0 cal. ka BP, the rate of driftwood delivery to the western Arctic islands was low (~1 recorded stranding event per 200 years) and intermittent, with the longest break in the record occurring between c. 3.0 and 5.0 cal. ka BP. This 2000‐year hiatus is attributed to a period of colder temperatures causing severe sea‐ice conditions and effectively making the coasts of the western Arctic islands inaccessible. After c. 1.0 cal. ka BP, driftwood incursion increased to maximum Holocene levels (~1 recorded stranding event every 20 years). Driftwood identified to the genus level as Larix that was delivered at this time suggests that the Trans Polar Drift current was regularly in its most southwestern position, related to a dominantly positive Arctic Oscillation mode. The Little Ice Age appears to have had little impact on driftwood entry to the western Canadian Arctic Archipelago, indeed the general abundance in the latest Holocene may record infrequent landfast sea ice.     

Advance,deglacial and sea‐level chronology for Foxe Peninsula,Baffin Island,Nunavut

The impact of the Laurentide Ice Sheet (LIS) deglaciation on Northern Hemisphere early Holocene climate can be evaluated only once a detailed chronology of ice history and sea‐level change is established. Foxe Peninsula is ideally situated on the northern boundary of Hudson Strait, and preserves a chronostratigraphy that provides important glaciological insights regarding changes in ice‐sheet position and relative sea level before and after the 8.2 ka cooling event. We utilized a combination of radiocarbon ages, adjusted with a new locally derived ΔR, and terrestrial in‐situ cosmogenic nuclide (TCN) exposure ages to develop a chronology for early‐Holocene events in the northern Hudson Strait. A marine limit at 192 m a.s.l., dated at 8.1–7.9 cal. ka BP, provides the timing of deglaciation following the 8.2 ka event, confirming that ice persisted at least north of Hudson Bay until then. A moraine complex and esker morphosequence, the Foxe Moraine, relates to glaciomarine outwash deltas and beaches at 160 m a.s.l., and is tightly dated at 7.6 cal. ka BP with a combination of shell dates and exposure ages on boulders. The final rapid collapse of Foxe Peninsula ice occurred by 7.1–6.9 cal. ka BP (radiocarbon dates and TCN depth profile age on an outwash delta), which supports the hypothesis that LIS melting contributed to the contemporaneous global sea‐level rise known as the Catastrophic Rise Event 3 (CRE‐3).     

Subarctic Front migration at the Reykjanes Ridge during the mid‐ to late Holocene: evidence from planktic foraminifera

Expansion of fresh and sea‐ice loaded surface waters from the Arctic Ocean into the sub‐polar North Atlantic is suggested to modulate the northward heat transport within the North Atlantic Current (NAC). The Reykjanes Ridge south of Iceland is a suitable area to reconstruct changes in the mid‐ to late Holocene fresh and sea‐ice loaded surface water expansion, which is marked by the Subarctic Front (SAF). Here, shifts in the location of the SAF result from the interaction of freshwater expansion and inflow of warmer and saline (NAC) waters to the Ridge. Using planktic foraminiferal assemblage and concentration data from a marine sediment core on the eastern Reykjanes Ridge elucidates SAF location changes and thus, changes in the water‐mass composition (upper ˜200 m) during the last c. 5.8 ka BP. Our foraminifer data highlight a late Holocene shift (at c. 3.0 ka BP) in water‐mass composition at the Reykjanes Ridge, which reflects the occurrence of cooler and fresher surface waters when compared to the mid‐Holocene. We document two phases of SAF presence at the study site: from (i) c. 5.5 to 5.0 ka BP and (ii) c. 2.7 to 1.5 ka BP. Both phases are characterized by marked increases in the planktic foraminiferal concentration, which coincides with freshwater expansions and warm subsurface water conditions within the sub‐polar North Atlantic. We link the SAF changes, from c. 2.7 to 1.5 ka BP, to a strengthening of the East Greenland Current and a warming in the NAC, as identified by various studies underlying these two currents. From c. 1.5 ka BP onwards, we record a prominent subsurface cooling and continued occurrence of fresh and sea‐ice loaded surface waters at the study site. This implies that the SAF migrated to the southeast of our core site during the last millennium.     

Palaeoenvironmental changes of the last two millennia on the western and northern Svalbard shelf

The western and northern Svalbard continental margins (European Arctic) are environmentally sensitive areas that are dependent on the northward flow of Atlantic Water, the largest heat source of the Arctic Ocean. Two marine sediment records from the Svalbard shelf: Kongsfjorden Trough and Hinlopen Trough, were analysed with regard to the benthic foraminiferal content and lithology to assess the palaeoceanographic evolution during the past two millennia with decadal to multi‐decadal temporal resolution. In both records, an overall gradual decrease of E. excavatum f. clavata during the past two millennia reflects a change towards generally warmer and less glacially influenced conditions, presumably related to enhanced inflow of Atlantic Water (AW). The influence of AW also varied on centennial time scales, as evidenced by faunal and sedimentary shifts occurring almost synchronously at both locations. The period from AD 700 to 1200 was characterized by enhanced inflow of AW, followed by the development of highly productive oceanographic fronts at both localities from AD 1200 to 1500. In contrast, the subsequent interval (AD 1500–1900) shows particularly harsh conditions in the Hinlopen Trough, with significantly reduced foraminiferal flux and sediment input related to perennial sea ice cover. In Kongsfjorden, less severe conditions were observed, indicating that the AW advection continued. The synchronicity of changes in both records demonstrates the effect of the variability in inflow of AW to the Svalbard region during the past 2000 years. Moreover, the records seem to follow climate anomalies, for example the Little Ice Age and Medieval Warm Period, found in the North Atlantic realm.     

Chronology and extent of the Lofoten–Vesterålen sector of the Scandinavian Ice Sheet from 26 to 16 cal. ka BP

The interplay between the onshore and offshore areas during the Last Glacial Maximum and the deglaciation of the Scandinavian Ice Sheet is poorly known. In this paper we present new results on the glacial morphology, stratigraphy and chronology of Andøya, and the glacial morphology of the nearby continental shelf off Lofoten–Vesterålen. The results were used to develop a new model for the timing and extent of the Scandinavian Ice Sheet in the study area during the local last glacial maximum (LLGM) (26 to 16 cal. ka BP). We subdivided the LLGM in this area into five glacial events: before 24, c. 23 to 22.2, 22.2 to c. 18.6, 18 to 17.5, and 16.9–16.3 cal. ka BP. The extent of the Scandinavian Ice Sheet during these various events was reconstructed for the shelf areas off Lofoten, Vesterålen and Troms. Icecaps survived in coastal areas of Vesterålen–Lofoten after the shelf was deglaciated and off Andøya ice flowed landwards from the shelf. During the LLGM the relative sea level was stable until 18.5 cal. ka BP, and thereafter there was a sea‐level drop on Andøya. Thus, relative sea level (i.e. a sea level rise) does not seem to be a driving mechanism for ice‐margin retreat in this area but the fall in sea level may have had some importance for the grounding episodes on the banks during deglaciation. The positions of the grounding zone wedges (GZWs) in the troughs are related to the morphology as they are often located where the troughs narrow.     

Late Quaternary (Marine Isotope Stage 3 to Recent) sedimentary evolution of the Basque shelf (southern Bay of Biscay)

Late Quaternary (MIS 3 to Recent) oceanographic evolution of the Basque shelf has been analysed for the first time based on the sedimentological analysis of three cores obtained from the middle and outer shelves. The cores are located in two interfluves separated by the San Sebastian canyon. The variability of the percentage of the planktonic foraminifera species Neogloboquadrina pachyderma sin. and of δ¹⁸O_bull allowed us to identify the influence of colder and warmer waters in the Basque shelf during the late Quaternary. From ～56 cal. ka BP to the end of the Last Glacial Maximum (19 cal. ka BP) the sedimentary record shows a decreasing trend in the mean grain size that correlates with the eustatic sea‐level fall. The last Deglaciation (19–11.5 cal. ka BP) is characterized by a sea‐level rise that produced an important hiatus in the western outer shelf. During the Holocene, the middle and outer shelves present different behaviours. From 11.5 to 6.7 cal. ka BP, in the outer shelf the sea‐level rise that started during the Deglaciation produced a hiatus, whereas in the middle shelf the sedimentary succession records the presence of warm to temperate waters. Between 6.7–4.9 cal. ka BP, the entrance of cold surface water‐masses that only affected the middle shelf has been identified, and temperate to warm waters occurred in the outer shelf. The cold surface water‐masses retreated during 4.9–4.3 cal. ka BP in the middle shelf. Finally, from 4.3 cal. ka BP to Recent, the middle shelf registers a hiatus due to sea‐level stabilization after a generalized transgression, synchronous to a decrease in the energy of the water‐masses in the outer shelf. In conclusion, the environmental changes detected in the Basque shelf are attributed to both regional and eustatic sea‐level changes.     

Palaeoceanographic changes in the northern Barents Sea during the last 16 000 years – new constraints on the last deglaciation of the Svalbard–Barents Sea Ice Sheet

The sediment core NP05‐71GC, retrieved from 360 m water depth south of Kvitøya, northwestern Barents Sea, was investigated for the distribution of benthic and planktic foraminifera, stable isotopes and sedimentological parameters to reconstruct palaeoceanographic changes and the growth and retreat of the Svalbard–Barents Sea Ice Sheet during the last ～16 000 years. The purpose is to gain better insight into the timing and variability of ocean circulation, climatic changes and ice‐sheet behaviour during the deglaciation and the Holocene. The results show that glaciomarine sedimentation commenced c. 16 000 a BP, indicating that the ice sheet had retreated from its maximum position at the shelf edge around Svalbard before that time. A strong subsurface influx of Atlantic‐derived bottom water occurred from 14 600 a BP during the Bølling and Allerød interstadials and lasted until the onset of the Younger Dryas cooling. In the Younger Dryas cold interval, the sea surface was covered by near‐permanent sea ice. The early Holocene, 11 700–11 000 a BP, was influenced by meltwater, followed by a strong inflow of highly saline and chilled Atlantic Water until c. 8600 a BP. From 8600 to 7600 a BP, faunal and isotopic evidence indicates cooling and a weaker flow of the Atlantic Water followed by a stronger influence of Atlantic Water until c. 6000 a BP. Thereafter, the environment generally deteriorated. Our results imply that (i) the deglaciation occurred earlier in this area than previously thought, and (ii) the Younger Dryas ice sheet was smaller than indicated by previous reconstructions.     

Chronology of the last deglaciation and Holocene environmental changes in the Sisimiut area,SW Greenland based on lacustrine records

The Sisimiut area was deglaciated in the early Holocene, c. 11 cal. ka BP. At that time the lowlands were inundated by the sea, but the isostatic rebound surpassed the global sea‐level rise, and the lowlands emerged from the sea. The pioneer vegetation in the area consisted of mosses and herbaceous plants. The oldest remains of woody plants (Empetrum nigrum) are dated to c. 10.3 cal. ka BP, and remains of Salix herbacea and Harrimanella hypnoides are found in slightly younger sediments. The maximum occurrence of statoblasts of the bryozoan Plumatella repens from c. 10 to 4.5 cal. ka BP probably reflects the Holocene thermal maximum, which is also indicated in geochemical proxies of the lake sediments. A maximum in organic matter accumulation in one of the three studied lakes c. 3 cal. ka BP can probably be ascribed to a late Holocene short‐duration temperature maximum or a period of increased aridity. Cenococcum geophilum sclerotia are common in the late Holocene, implying increased soil erosion during the Neoglaciation. A comparison with sediment and macrofossil records from inland shows similar Holocene trends and a similar immigration history. It also reveals that there has been a significant gradient throughout the Holocene, from an oceanic and stable climate at the outer coast to a more continental and unstable climate with warmer summers and drier conditions close to the margin of the Greenland ice sheet, where the buffer capacity of the sea is lower.     

Retreat of the Smith Sound Ice Stream in the Early Holocene

Nares Strait, a major connection between the Arctic Ocean and Baffin Bay, was blocked by coalescent Innuitian and Greenland ice sheets during the last glaciation. This paper focuses on the events and processes leading to the opening of the strait and the environmental response to establishment of the Arctic‐Atlantic throughflow. The study is based on sedimentological, mineralogical and foraminiferal analyses of radiocarbon‐dated cores 2001LSSL‐0014PC and TC from northern Baffin Bay. Radiocarbon dates on benthic foraminifera were calibrated with ΔR = 220±20 years. Basal compact pebbly mud is interpreted as a subglacial deposit formed by glacial overriding of unconsolidated marine sediments. It is overlain by ice‐proximal (red/grey laminated, ice‐proximal glaciomarine unit barren of foraminifera and containing >2 mm clasts interpreted as ice‐rafted debris) to ice‐distal (calcareous, grey pebbly mud with foraminifera indicative of a stratified water column with chilled Atlantic Water fauna and species associated with perennial and then seasonal sea ice cover) glacial marine sediment units. The age model indicates ice retreat into Smith Sound as early as c. 11.7 and as late as c. 11.2 cal. ka BP followed by progressively more distal glaciomarine conditions as the ice margin retreated toward the Kennedy Channel. We hypothesize that a distinct IRD layer deposited between 9.3 and 9 (9.4–8.9 1σ) cal. ka BP marks the break‐up of ice in Kennedy Channel resulting in the opening of Nares Strait as an Arctic‐Atlantic throughflow. Overlying foraminiferal assemblages indicate enhanced marine productivity consistent with entry of nutrient‐rich Arctic Surface Water. A pronounced rise in agglutinated foraminifers and sand‐sized diatoms, and loss of detrital calcite characterize the uppermost bioturbated mud, which was deposited after 4.8 (3.67–5.55 1σ) cal. ka BP. The timing of the transition is poorly resolved as it coincides with the slow sedimentation rates that ensued after the ice margins retreated onto land.     

Influence of the Laurentide Ice Sheet and relative sea‐level changes on sediment dynamics in the Estuary and Gulf of St. Lawrence since the last deglaciation

Physical properties, grain size, bulk mineralogy, elemental geochemistry and magnetic parameters of three sediment piston cores recovered in the Laurentian Channel from its head to its mouth were investigated to reconstruct changes in detrital sediment provenance and transport related to climate variability since the last deglaciation. The comparison of the detrital proxies indicates the succession of two sedimentary regimes in the Estuary and Gulf of St. Lawrence (EGSL) during the Holocene, which are associated with the melting history of the Laurentide Ice Sheet (LIS) and relative sea‐level changes. During the early Holocene (10–8.5 cal. ka BP), high sedimentation rates together with mineralogical, geochemical and magnetic signatures indicate that sedimentation in the EGSL was mainly controlled by meltwater discharges from the local retreat of the southeastern margin of the LIS on the Canadian Shield. At this time, sediment‐laden meltwater plumes caused the accumulation of fine‐grained sediments in the ice‐distal zones. Since the mid‐Holocene, postglacial movements of the continental crust, related to the withdrawal of the LIS (c. 6 cal. ka BP), have triggered significant variations in relative sea level (RSL) in the EGSL. The significant correlation between the RSL curves and the mineralogical, geochemical, magnetic and grain‐size data suggest that the RSL was the dominant force acting on the sedimentary dynamics of the EGSL during the mid‐to‐late Holocene. Beyond 6 cal. ka BP, characteristic mineralogical, geochemical, magnetic signatures and diffuse spectral reflectance data suggest that the Canadian Maritime Provinces and western Newfoundland coast are the primary sources for detrital sediments in the Gulf of St. Lawrence, with the Canadian Shield acting as a secondary source. Conversely, in the lower St. Lawrence Estuary, detrital sediments are mainly supplied by the Canadian Shield province. Finally, our results suggest that the modern sedimentation regime in the EGSL was established during the mid‐Holocene.     

Changes in the inflow of saline water into the Bornholm Basin (SW Baltic Sea) during the past 7100 years – evidence from benthic foraminifera record

The Baltic Sea (~393 000 km²) is the largest brackish sea in the world and its hydrographic and environmental conditions are strongly dependent on the frequency of saline water inflows from the North Sea. To improve our understanding of the natural variability of the Baltic Sea ecosystem detailed reconstructions of past saline water inflow changes based on palaeoecological archives are needed. Here we present a high‐resolution study of benthic foraminiferal assemblages accompanied by sediment geochemistry (loss on ignition, total organic carbon) and other microfossil data (ostracods and cladocerans) from a well‐dated 8‐m‐long gravity core taken in the Bornholm Basin. The foraminiferal diversity in the core is low and dominated by species of Elphidium. The benthic foraminiferal faunas in the central Baltic require oxic bottom water conditions and salinities >11–12 PSU. Consequently, shell abundance peaks in the record reflect frequent saline water inflow phases. The first appearance of foraminiferal tests and ostracods in the investigated sediment core is dated to c. 6.9 cal. ka BP and attributed to the first inflows of saline and oxygenated bottom waters into the Bornholm Basin during the Littorina Sea transgression. The transgression terminated the Ancylus Lake phase, reflected in the studied record by abundant cladocerans. High absolute foraminiferal abundances are found within two time intervals: (i) c. 5.5–4.0 cal. ka BP (Holocene Thermal Maximum) and (ii) c. 1.3–0.75 cal. ka BP (Medieval Climate Anomaly). Our data also show three intervals of absent or low saline water inflows: (i) c. 6.5–6.0 cal. ka BP, (ii) c. 3.0–2.3 cal. ka BP and (iii) c. 0.5–0.1 cal. ka BP (Little Ice Age). Our study demonstrates a strong effect of saline and well‐oxygenated water inflows from the Atlantic Ocean on the Baltic Sea ecosystem over millennial time scales, which is linked to the major climate transitions over the last 7 ka.     

Reconstruction of the Late Quaternary Glaciation of the Macha Khola valley (Gorkha Himal, Nepal) using relative and absolute (C, Be, dendrochronology) dating techniques

Late Quaternary glacier fluctuations in the Macha Khola valley (Gorkha Himal, Nepal) were reconstructed using relative and absolute dating techniques. Our results indicate that younger moraine complexes were left by Late Holocene (<1.7 cal. ka BP), mid-Holocene (ca 3 cal. ka BP), and Lateglacial (ca 13 cal. ka BP) ice advances. Older Late Quaternary glacier advances occurred during Marine Oxygen Isotope Stages (MIS) 2 and 3–4. No relics of Middle or Early Pleistocene glaciations could be found. During MIS 3–4, glaciers advanced down to an altitude of at least 2150 m a.s.l., corresponding to an ELA depression of approximately 1300 m. At about 3500 m a.s.l., the MIS 2 Macha Khola glacier reached almost the thickness of the former MIS 3–4 glacier and retreated some time before 17.9 cal. ka BP. The Lateglacial glacier advanced again several times to altitudes between 2450 and 3400 m a.s.l. The mid-Holocene glaciers extended much farther down-valley than the Late Holocene ones. Dendrochronological data of Abies spectabilis suggested several periods of unfavourable growth conditions especially at the beginning of the 19th (1820) and 20th (1905) centuries.     

Vegetation and climate changes in northwestern Russia during the Lateglacial and Holocene inferred from the Lake Ladoga pollen record

The new pollen record from the upper 12.75 m of a sediment core obtained in Lake Ladoga documents regional vegetation and climate changes in northwestern Russia over the last 13.9 cal. ka. The Lateglacial chronostratigraphy is based on varve chronology, while the Holocene stratigraphy is based on AMS ¹⁴C and OSL dates, supported by comparison with regional pollen records. During the Lateglacial (c. 13.9–11.2 cal. ka BP), the Lake Ladoga region experienced several climatic fluctuations as reflected in vegetation changes. Shrub and grass communities dominated between c. 13.9 and 13.2 cal. ka BP. The increase in Picea pollen at c. 13.2 cal. ka BP probably reflects the appearance of spruce in the southern Ladoga region at the beginning of the Allerød interstadial. After c. 12.6 cal. ka BP, the Younger Dryas cooling caused a significant decrease in spruce and increase in Artemisia with other herbs, indicative of tundra‐ and steppe‐like vegetation. A sharp transition from tundra‐steppe habitats to sparse birch forests characterizes the onset of Holocene warming c. 11.2 cal. ka BP. Pine forests dominated in the region from c. 9.0 to 8.1 cal. ka BP. The most favourable climatic conditions for deciduous broad‐leaved taxa existed between c. 8.1 and 5.5 cal. ka BP. Alder experiences an abrupt increase in the local vegetation c. 7.8 cal. ka BP. The decrease in tree pollen taxa (especially Picea) and the increase in herbs (mainly Poaceae) probably reflect human activity during the last 2.2 cal. ka. Pine forests have dominated the region since that time. Secale and other Cerealia pollen as well as ruderal herbs are permanently recorded since c. 0.8 cal. ka BP.     

Glacial and environmental changes over the last 60 000 years in the Polar Ural Mountains,Arctic Russia,inferred from a high‐resolution lake record and other observations from adjacent areas

Our knowledge about the glaciation history in the Russian Arctic has to a large extent been based on geomorphological mapping supplemented by studies of short stratigraphical sequences found in exposed sections. Here we present new geochronological data from the Polar Ural Mountains along with a high‐resolution sediment record from Bolshoye Shchuchye, the largest and deepest lake in the mountain range. Seismic profiles show that the lake contains a 160‐m‐thick sequence of unconsolidated lacustrine sediments. A well‐dated 24‐m‐long core from the southern end of the lake spans the last 24 cal. ka. From downward extrapolation of sedimentation rates we estimate that sedimentation started about 50–60 ka ago, most likely just after a large glacier had eroded older sediments from the basin. Terrestrial cosmogenic nuclide (TCN) exposure dating (¹⁰Be) of boulders and Optically Stimulated Luminescence (OSL) dating of sediments indicate that this part of the Ural Mountains was last covered by a coherent ice‐field complex during Marine Isotope Stage (MIS) 4. A regrowth of the glaciers took place during a late stage of MIS 3, but the central valleys remained ice free until the present. The presence of small‐ and medium‐sized glaciers during MIS 2 is reflected by a sequence of glacial varves and a high sedimentation rate in the lake basin and likewise from ¹⁰Be dating of glacial boulders. The maximum extent of the mountain glaciers during MIS 2 was attained prior to 24 cal. ka BP. Some small present‐day glaciers, which are now disappearing completely due to climate warming, were only slightly larger during the Last Glacial Maximum (LGM) as compared to AD 1953. A marked decrease in sedimentation rate around 18–17 cal. ka BP indicates that the glaciers then became smaller and probably disappeared altogether around 15–14 cal. ka BP.     

Late Younger Dryas and early Holocene palaeoenvironments in the Skagerrak,eastern North Atlantic: a multiproxy study

Erbs‐Hansen, D. R., Knudsen, K. L., Gary, A. C., Jansen, E., Gyllencreutz, R., Scao, V. & Lambeck, K. 2011: Late Younger Dryas and early Holocene palaeoenvironments in the Skagerrak, eastern North Atlantic: a multiproxy study. Boreas, 10.1111/j.1502‐3885.2011.00205.x. ISSN 0300‐9843 A high‐resolution study of palaeoenvironmental changes through the late Younger Dryas and early Holocene in the Skagerrak, the eastern North Atlantic, is based on multiproxy analyses of core MD99‐2286 combined with palaeowater depth modelling for the area. The late Younger Dryas was characterized by a cold ice‐distal benthic foraminiferal fauna. After the transition to the Preboreal (c. 11 650 cal. a BP) this fauna was replaced by a Cassidulina neoteretis‐dominated fauna, indicating the influence of chilled Atlantic Water at the sea floor. Persisting relatively cold bottom‐water conditions until c. 10 300 cal. a BP are presumably a result of an outflow of glacial meltwater from the Baltic area across south‐central Sweden, which led to a strong stratification of the water column at MD99‐2286, as also indicated by C. neoteretis. A short‐term peak in the C/N ratio at c. 10 200 cal. a BP is suggested to indicate input of terrestrial material, which may represent the drainage of an ice‐dammed lake in southern Norway, the Glomma event. After the last drainage route across south‐central Sweden closed, c. 10 300 cal. a BP, the meltwater influence diminished, and the Skagerrak resembled a fjord with a stable inflow of waters from the North Atlantic through the Norwegian Trench and a gradual increase in boreal species. Full interglacial conditions were established at the sea floor from c. 9250 cal. a BP. Subsequent warm stable conditions were interrupted by a short‐term cooling around 8300–8200 cal. a BP, representing the 8.2 ka event.     

Holocene lake sediments from the Faiyum Oasis in Egypt: a record of environmental and climate change

The Qarun Lake in the Faiyum Oasis (Egypt) provides a unique record of Holocene environmental and climate change in an arid area largely devoid of fossil proxy records. Multiple lithological, palaeontological and geochemical proxies and 32 radiocarbon dates from the 26‐m‐long core FA‐1 provide a time series of the lake's transformation. Our results confirm that a permanent lake appeared in the Holocene at c. 10 cal. ka BP. The finely laminated lake sediments consist of diatomite, in which diatoms and ostracods together with lower concentrations of ions indicate a freshwater environment at the end of the early and middle Holocene. This freshwater supply was closely associated with regular inflows of the Nile water during flood seasons, when the Intertropical Convergence Zone (ITCZ) migrated northwards in Africa, although it has probably never reached the Faiyum Oasis. Local rainfall, possibly connected with a northern atmospheric circulation, may have been important during winter. Several phases in the lake's evolution are recognized, represented by oscillations between deep open freshwater conditions during more humid climate and shallow fresh to brackish water during drier episodes. After a long freshwater phase, the lake setting has become more brackish since c. 6.2 cal. ka BP as indicated by diatoms and increasing contents of evaporite ions in the sediment. This clearly shows that since that time the lake has occasionally become partly desiccated. This is a result of reduced discharge of the Nile. In the late Holocene the lake was mostly brackish and then gradually turned into a saline lake. This natural process was interrupted about 2.3 cal. ka BP when a man‐made canal facilitated water inflow from the Nile. The examined FA‐1 core can be used as a reference age model of climate change in the Holocene and its impact on the development and decline of ancient civilizations in northeastern Africa.