Advection of Atlantic Water to the western and northern Svalbard shelf since 17,500 cal yr BP

The changes in flow and character of the warm Atlantic Water through the last 17,500 cal yr are reconstructed from the distribution of benthic foraminifera species, planktonic and benthic foraminifera abundances, stable oxygen isotopes and lithology in two cores from the western and northern shelf of Svalbard. The results show almost continuous presence of Atlantic Water at the shelf areas since >14,500 cal yr BP. The Bølling and Allerød intervals stand out as periods of highest bottom waters temperatures. The strong inflow of saline, but chilled Atlantic Water during the early Holocene was followed by cooling and freshening of the bottom waters during the mid- and late Holocene. The two records reveal synchronous oceanographic changes that are closely tied to changes in the flow of Atlantic Water recorded further south in the Nordic seas. The early Holocene warming was not just an effect of higher solar insolation, but was also due to increased heat flux from the stronger Atlantic Water inflow driven by wind force and/or thermohaline circulation.     

Major changes in ice stream dynamics during deglaciation of the north-western margin of the Laurentide Ice Sheet

Victoria Island lies at the north-western limit of the former North American (Laurentide) Ice Sheet in the Canadian Arctic Archipelago and displays numerous cross-cutting glacial lineations. Previous work suggests that several ice streams operated in this region during the last (Wisconsinan) glaciation and played a major role in ice sheet dynamics and the delivery of icebergs into the Arctic Ocean. This paper produces the first detailed synthesis of their behaviour from the Last Glacial Maximum through to deglaciation (～21–9.5 cal ka BP) based on new mapping and a previously published radiocarbon-constrained ice sheet margin chronology. Over 70 discrete ice flow events (flow-sets) are ‘fitted’ to the ice margin configuration to allow identification of several ice streams ranging in size from large and long-lived (thousands of years) to much smaller and short-lived (hundreds of years). The reconstruction depicts major ice streams in M'Clure Strait and Amundsen Gulf which underwent relatively rapid retreat from the continental shelf edge at some time between ～15.2 and 14.1 cal ka BP: a period which encompasses climatic warming and rapid sea level rise (meltwater pulse-1a). Following this, overall retreat was slower and the ice streams exhibited asynchronous behaviour. The Amundsen Gulf Ice Stream continued to operate during ice margin retreat, whereas the M'Clure Strait Ice Stream ceased operating and was replaced by an ice divide within ～1000 years. This ice divide was subsequently obliterated by another short-lived phase of ice streaming in M'Clintock Channel ～13 cal ka BP. The timing of this large ice discharge event coincides with the onset of the Younger Dryas. Subsequently, a minor ice divide developed once again in M'Clintock Channel, before final deglaciation of the island shortly after 9.5 cal ka BP. It is concluded that large ice streams at the NW margin of the Laurentide Ice Sheet, equivalent in size to the Hudson Strait Ice Stream, underwent major changes during deglaciation, resulting in punctuated delivery of icebergs into the Arctic Ocean. Published radiocarbon dates constrain this punctuated delivery, as far as is possible within the limits imposed by their precision, and we note their coincidence with pulses of meltwater delivery inferred from numerical modelling and ocean sediment cores.     

Testing models of mid to late Holocene sea-level change,North Queensland,Australia

Understanding the nature of global ice-equivalent eustatic sea-level changes during the mid to late Holocene is important to our understanding of how ice sheets will respond to future climate change. This study re-analyses the indicative meaning and age control of existing relative sea-level (RSL) data from Cleveland Bay, North Queensland, Australia and presents new RSL data from a foraminifera-based transfer function as a preliminary test of global geophysical models in this region during the mid to late Holocene. The foraminifera-based transfer function produces reliable RSL estimates, consistent through the mid to late Holocene at different locations in Cleveland Bay. Analysis of the combined RSL database reveals that RSL rose above present between 8 and 6.2 ka cal. BP, with the peak of the sea-level highstand c. 2.8 m above present at c. 5 ka cal. BP, remaining relatively stable above +1.5 m from 6.2 until at least 2.3 ka cal. BP, falling to present in the last millennia. This long period of sea level above present in the mid to late Holocene suggests a gradual rather than abrupt end to global ice melt, which must have continued into the late Holocene. This new analysis also shows no evidence for episodic fluctuations within the highstand, although they cannot be entirely ruled out by this study. This study demonstrates that more sea-level data needs to be collected from locations uncontaminated by glacio-isostasy, hydro-isostasy and tectonic effects, in order to better constrain the late Holocene melt histories of the large polar ice sheets.     

A ∼25 ka Indian Ocean monsoon variability record from the Andaman Sea

Recent paleoclimatic work on terrestrial and marine deposits from Asia and the Indian Ocean has indicated abrupt changes in the strength of the Asian monsoon during the last deglaciation. Comparison of marine paleoclimate records that track salinity changes from Asian rivers can help evaluate the coherence of the Indian Ocean monsoon (IOM) with the larger Asian monsoon. Here we present paired Mg/Ca and δ¹⁸O data on the planktic foraminifer Globigerinoides ruber (white) from Andaman Sea core RC12-344 that provide records of sea-surface temperature (SST) and δ¹⁸O of seawater (δ¹⁸O_sw) over the past 25,000 years (ka) before present (BP). Age control is based on nine accelerator mass spectrometry (AMS) dates on mixed planktic foraminifera. Mg/Ca-SST data indicate that SST was ∼3 °C cooler during the last glacial maximum (LGM) than the late Holocene. Andaman Sea δ¹⁸O_sw exhibited higher than present values during the Lateglacial interval ca 19–15 ka BP and briefly during the Younger Dryas ca 12 ka BP. Lower than present δ¹⁸O_sw values during the BØlling/AllerØd ca 14.5–12.6 ka BP and during the early Holocene ca 10.8–5.5 ka BP are interpreted to indicate lower salinity, reflect some combination of decreased evaporation–precipitation (E–P) over the Andaman Sea and increased Irrawaddy River outflow. Our results are consistent with the suggestion that IOM intensity was stronger than present during the BØlling/AllerØd and early Holocene, and weaker during the late glaciation, Younger Dryas, and the late Holocene. These findings support the hypothesis that rapid climate change during the last deglaciation and Holocene included substantial hydrologic changes in the IOM system that were coherent with the larger Asian monsoon.     

Sedimentation history of the northern North Sea Margin during the last 150 ka

The Norwegian Channel Ice Stream (NCIS) is one the defining features of the Fennoscandian icesheet. Still little is known of the detailed dynamics of this ice stream in relation to regional changes in ice cover, paleoceanographic and climatic changes. Sedimentological data from core MD99-2283 in combination with seismic data allow a detailed chronological reconstruction of the outbuilding of the margin and the ice extent in southern Scandinavia through the last 150 ka. An integrated stratigraphy of the margin is presented and compared to the glacial history. Changes in the regional ice cover are reflected in the accumulation rates, the clay mineralogy, the coarse chalk fraction and the number of IRD >2 mm in core MD99-2283, while the sedimentation on the North Sea Fan as derived from seismic data provides direct evidence for the glacial activity at the shelf edge. Tentative evidence was found for two Early Weichselian glacial advances in southern Scandinavia and possibly Scotland at around 110 and 80 ka BP. From 42 cal ka BP the ice cover expanded in southern Fennoscandia and led to increased deposition on the margin and the occurrence of local melt water outbursts. Significantly increased accumulation rates, coarse chalk, local meltwater output and smectite occur during the ice expansion in the North Sea from around 34 cal ka BP. The main outbuilding phase of the NSF during the last glacial cycle occurred after 30 cal ka BP. From around 24 cal ka BP the NCIS became highly active and advanced at least three times prior to the final retreat from the shelf edge around 19.0 cal ka BP.     

The Allerød–Younger Dryas–Holocene sequence in the west-central Champlain Sea,eastern Ontario: a record of glacial,oceanographic, and climatic changes

The aragonite mineralogy and geochemistry of the mollusc faunas preserved at Navan and Bearbrook, Ontario, serve as proxies of original seawater chemistry. The composite section spanning 12,980–10,980 cal yr BP includes the Younger Dryas (YD) paleoclimatic oscillation. Oxygen isotopes demonstrate the onset of cooling with the YD event, in addition to the lowering of marine values by the influx of isotopically light glacial meltwater from Lake Agassiz. Impact of cooling and dilution is reduced or eliminated with the start of the Holocene, when water temperatures and salinities for Champlain Sea (CS) seawater were 8–16 °C and 27–34 ppt, respectively. Overall, oxygen isotope values deceased to −3.5% during the YD mainly due to freshening by glacial meltwater. Carbon isotopes confirm the rise in atmospheric CO₂ concentration at the YD–Holocene transition. Marine strontium isotope values for the Allerød–YD–earliest Holocene range from 0.709151 (16,210 cal yr BP) to 0.709145 (12,980 cal yr BP) and 0.709142 (10,950 cal yr BP). The oceanographic changes recorded for the CS are in agreement with the evolutionary phases of Lake Agassiz and deglaciation dynamics of the Laurentide Ice Sheet. The volume and direction of meltwater discharge from Lake Agassiz alternated between the Gulf of Mexico during the Allerød, via the Great Lakes through the CS to the North Atlantic during the YD, and back to the Gulf of Mexico during the early Holocene, but with diminished impact.     

Fluvio–sedimentary response of the monsoon-fed Indian rivers to Late Pleistocene–Holocene changes in monsoon strength: reconstruction based on existing 14C dates

The primary objective of the present study is to identify major phases of alluviation in the Indian region since the abrupt Deglacial intensification of the monsoon (∼15 cal ka BP) on the basis of analysis of 68 radiocarbon dates from two major hydro-geomorphic regions of India: the Central Ganga Basin (CGB) and the Deccan Peninsula (DP). The recognition of main phases of alluviation and incision has been achieved by evaluating the temporal distribution and clustering of the radiocarbon dates from alluvial sequences. The clusters were detected on the basis of the interpretation of the summed probability distribution plots derived by using OxCal version 4.0.1 and CALPAL (version May 2006) software packages.The summed probability plots reveal that periods of alluviation in the CGB, represented by three clusters (13.9–12.3, 11.9–11.2 and 9.8–9.0 cal ka BP) occur roughly before the onset of Early Holocene monsoon optimum phase. Two other clusters occur in the intervals 3.6–2.8 and 1.1–0.9 cal ka BP. The peak monsoon period generally lacks clusters of radiocarbon dates implying fluvial erosion and channel incision. This period also shows clustering of radiocarbon dates of the abandoned channels. In comparison, ¹⁴C dates from DP alluvial units form clusters at 16.4–14, 12.8–11.2, 10.8–8.9, 8.1–6.7 and 5.1–3.9 cal ka BP, indicating an association with the Deglacial–Early Holocene humid phase. Alluviation in the DP appears to have continued, more or less, uninterrupted till the middle of the Holocene epoch. The beginning and end of the discernible gap in the radiocarbon dates of CGB (9.0–3.6 cal ka) broadly corresponds with the two well-established short-term events of the Holocene, 8.2 and 4.2 ka cal BP. In comparison, the prominent gap of DP radiocarbon dates (3.9–2.1 ka cal BP) approximately begins with the 4.2 ka cal BP short-term event (onset of aridity) and ends with the 2.0 ka cal BP enhanced monsoon event.Notwithstanding the inter-regional differences in the fluvio–sedimentary response in the India region, the clusters of radiocarbon dates indicate that the century to millennium scale variations in fluvial activity in the Indian subcontinent were intimately linked to long-term fluctuations in the monsoon strength during the Late Quaternary.     

Synchronous climate anomalies in the western North Pacific and North Atlantic regions during the last 14,000 years

A peat cellulose δ¹⁸O record spanning around 14,000 years from the Hani peat mire in northeastern China reveals several abrupt temperature anomalies in the period from the last deglaciation through the Holocene. The timing of these anomalies coincides well with the notable cooling events recorded respectively using the GISP2 ice core and ice-rafted sediment of the North Atlantic Ocean, such as the Older Dryas, Inter-Allerød, Younger Dryas, and the nine ice-rafted debris events. The results demonstrate that this repeating pattern of abrupt temperature deterioration is not limited to the North Atlantic area at high latitude but also exists in the western North Pacific region at middle latitude. The synchronous temperature anomalies possibly are resulted from the joint effects of meltwater discharge into the North Atlantic Ocean and reduced solar activity. In the period from around 8600 to 8200 cal. yrs BP the Hani peat record shows a broad δ¹⁸O peak that may reflect compound climate signals resulting from the two kinds of forcing factors: the temperature drop related to reduced solar activity at around 8600–8250 cal. yrs BP, and the temperature anomaly attributed to the meltwater effect at around 8220 ± 70 cal. yrs BP. This result may provide palaeo-temperature evidence for existence of the sharp “8.2 k” event in the western North Pacific region. In addition, our results have revealed that in the period from the last deglaciation through the Holocene the synchronous temperature anomalies before and after the “8.2 k” event seem to be related to meltwater outflow and reduced solar activity, respectively. It is important that the all temperature anomalies—whether because of reduced solar activity in the late Holocene or from meltwater discharge in the early Holocene—are accompanied by an abrupt decline in the Indian Ocean summer monsoon and abrupt strengthening of the East Asian summer monsoon. It is likely that reduced solar activity and meltwater outflow appear to modulate Earth system changes in the same direction. The influences could be compounded. Reduced solar activity and meltwater outburst both appear to act as triggers for occurrence of the El Niño phenomenon in the equatorial Pacific Ocean, which may result in broad teleconnections between the temperature anomaly in the Northern Hemisphere and abrupt variation of the Asian monsoon.     

Late Pleistocene submarine mass movements: occurrence and causes

An extensive study of Late Pleistocene continental slope submarine mass movements was undertaken. Twenty-six well-dated mass movements occurred during the last 45 ka BP in the North Atlantic sector. A latitudinal trend is observed: between 45 and 12 ka BP most events occur in the mid- to low-latitudes, post-12 ka BP high-latitude occurring events dominate. A cluster of events is associated with the Last Glacial sea level lowstand and Termination 1B. Further events are associated with Termination 1A and the Holocene. Prior to 23 ka BP no clear relationship with the ice core atmospheric methane record is observed, in contrast during and following the deglaciation there is a possible relationship with atmospheric methane. High-latitude mass movements are primarily controlled by cyrospheric-induced variations in sedimentation and local sea level. In high latitudes, the glaciation subdues mass movement activity through reduced seisimicity, sediment supply and ocean temperatures. Deglaciation increases the sediment supply, seisimicity and ocean temperatures, thus increasing the likelihood of continental slope failures. For example the Storegga event coincides with high isostatic uplift and postglacial seisimicity, while the Andøya and Trænadjupet events occur before and after the peak rates respectively. In contrast low latitudes experience greater risk of slope failures during glacial periods from falling sea levels, although during the deglacial and interglacial period there is a potential for failure from changes in deposition centres and rates, as well as warming ocean temperatures potentially leading to dissociation of gas hydrates. The ongoing rapid deglaciation of coastal Greenland and Antarctica and consequent rapid input of sediment, isostatic uplift, crustal stress release and warming bottom water temperature at the shelf break will increase the risk of continental slope failure in these regions.     

Climatic and environmental changes in north-western Russia between 15,000 and 8000 cal yr BP: a review

Multi-proxy palaeoenvironmental studies of nine sediment sequences from four areas in north-western Russia reveal significant changes in climate, lake productivity and vegetation during the Lateglacial and early Holocene that show some degree of correlation with changes reconstructed from sites throughout the North Atlantic region. At Lake Nero in the Rostov-Jaroslavl’ area, which is outside the maximum limit of the Scandinavian Ice Sheet, sedimentation recommenced shortly after 15 cal ka BP in response to increases in temperature and humidity during Greenland Interstadial 1 (GI-1; Bølling-Allerød). However, climatic amelioration during GI-1 was slow to increase lake organic productivity or trigger large-scale changes in much of northwestern Russia. In general, this region was characterised by long-lasting lake-ice cover, low lake productivity, soil erosion, and dwarf shrub and herb tundra until the end of Greenland Stadial 1 (GS-1; Younger Dryas). At some sites, distinct increases in lake organic productivity, mean summer temperatures and humidity and the expansion of forest trees coincide with rapid warming at the beginning of the Holocene and the increasing influence of warm air masses from the North Atlantic. At other sites, particularly on the Karelian Isthmus, but also in Russian Karelia, the delayed response of limnic and terrestrial environments to early Holocene warming is likely related to the cold surface waters of the Baltic Ice Lake, the proximity of the Scandinavian Ice Sheet and associated strengthened easterlies, and/or extensive permafrost and stagnant ice. These multi-proxy studies underscore the importance of local conditions in modifying the response of individual lakes and their catchments.While Lateglacial vegetation was dominated by Betula nana and Salix shrubs and various herbs, pollen and plant macrofossils suggest that Betula pubescens trees became established as early as 14–13 cal ka BP in the Rostov-Jaroslavl’ area. In general, our data sets suggest that trees migrated from the southeast to the west and then spread later to the northeast and northwest, paralleling the direction of ice retreat, with Betula pubescens immigrating first, followed by Pinus sylvestris and Picea abies. However, palaeoecological records from Lake Terebenskoye in the Valdai Highlands suggest that the arrival of Picea abies preceded other trees in that area and that it colonised tundra communities as early as 12 cal ka BP. Since Lateglacial vegetation change in north-western Russia was time-transgressive, independent measures of palaeoclimate (e.g., chironomid-based palaeotemperature estimates) are needed for this region.     

Sea ice variations in the central Canadian Arctic Archipelago during the Holocene

A sea ice record for Barrow Strait in the Canadian Arctic Archipelago (CAA) is presented for the interval 10.0–0.4 cal. kyr BP. This Holocene record is based primarily on the occurrence of a sea ice biomarker chemical, IP₂₅, isolated from a marine sediment core obtained from Barrow Strait in 2005. A core chronology is based on ¹⁴C AMS dating of mollusc shells obtained from ten horizons within the core. The primary IP₂₅ data are compared with complementary proxy data obtained from analysis of other organic biomarkers, stable isotope composition of bulk organic matter, benthic foraminifera, particle size distributions and ratios of inorganic elements. The combined proxy data show that the palaeo-sea ice record can be grouped according to four intervals, and these can be contextualised further with respect to the Holocene Thermal Maximum (HTM). Spring sea ice occurrence was lowest during the early–mid Holocene (10.0–6.0 cal. kyr BP) and this was followed by a second phase (6.0–4.0 cal. kyr BP) where spring sea ice occurrence showed a small increase. Between 4.0 and 3.0 cal. kyr BP, spring sea ice occurrence increased abruptly to above the median and we associate this interval with the termination of the HTM. Elevated spring sea ice occurrences continued from 3.0 to 0.4 cal. kyr BP, although they were more variable on shorter timescales. Within this fourth interval, we also provide evidence for slightly lower and subsequently higher spring sea ice occurrence during the Mediaeval Warm Period and the Little Ice Age respectively. Comparisons are made between our proxy data with those obtained from other palaeo-climate and sea ice studies for the CAA.     

Holocene glacier history of Bjørnbreen and climatic reconstruction in central Jotunheimen,Norway, based on proximal glaciofluvial stream-bank mires

Holocene variations of Bjørnbreen, Smørstabbtinden massif, west-central Jotunheimen are reconstructed from the lithostratigraphy of two alpine stream-bank mires flooded episodically by meltwater. The approach uses multiple sedimentological indicators (weight loss-on-ignition, mean grain size, grain-size fractions, bulk density, moisture content and magnetic susceptibility), an a priori model of overbank deposition of suspended glaciofluvial sediments, a detailed chronology based on 56 radiocarbon dates, and a Little Ice Age sedimentological analogue. Rapid, late-Preboreal deglaciation was indicated by immigration of Betula pubescens by 9700 cal. BP. An interval of at least 3000 years in the early Holocene when glaciers were absent was interrupted by two abrupt episodes of glacier expansion around the time of the Finse Event, the first at ca 8270–7900 cal. BP (Bjørnbreen I Event) and the second at ca 7770–7540 cal. BP (Bjørnbreen II Event). Neoglaciation began shortly before ca 5730 cal. BP with gradual build-up to the maximum of the Bjørnbreen III Event at ca 4420 cal. BP. Later maxima occurred at ca 2750 cal. BP (Bjørnbreen IV Event) and at 1300, 1260, 1060 and 790 cal. BP (all within the Bjørnbreen V Event). Glaciers were smaller than today and possibly melted away on several occasions in the late Holocene (ca 3950, 1410 and 750 cal. BP). Minor maxima also occurred at ca 660 and 540 cal. BP, within the late Mediaeval Warm Period and the early Little Ice Age, respectively. The Little Ice Age maximum was dated to 213±25 BP (ca 205 cal. BP). The relative magnitudes of the main glacier maxima were determined: Erdalen Event>Little Ice Age Event (Bjørnbreen VI)>Bjørnbreen I (Finse Event) ≈ Bjørnbreen II>Bjørnbreen V⩾Bjørnbreen IV>Bjørnbreen III. These episodic events of varying magnitude and abruptness were used in conjunction with an independent summer-temperature proxy to reconstruct variations in equilibrium-line altitude (ELA) and a Holocene record of winter precipitation. Since the Preboreal, ELA varied within a range of about 390 m, and winter precipitation ranged between 40 and 160% of modern values. Winter precipitation variations appear to have been the main cause of these century- to millennial-scale Holocene glacier variations.     

Late Quaternary climatic changes,and associated human responses,during the last ~ 45 000 yr in the Eastern and adjoining Western Cape,South Africa

Palaeoenvironmental evidence indicative of former climatic conditions in the Eastern and adjoining Western Cape during the last ~ 45 000 yr is presented and summarised. Interstadial conditions began before 43 000 BP but were succeeded by stadial conditions at ~ 24 000 BP. These climatic phases are designated the Birnam Interstadial and the Bottelnek Stadial after the type sites at which they were identified in the Eastern Cape. The Bottelnek Stadial apparently equates with the Last Glacial Maximum. Late Glacial warming was apparent by 18/17 000 BP. Sea level rose markedly by ~ 14 000 BP. Climatic oscillations marked the end of the Late Glacial. The Early Holocene was drier than the Late Holocene and, at least in the Drakensberg, there was marked aridity in the mid-Holocene. Human responses to these climatic events are briefly described.     

Hydrogeological modeling as a tool supporting the interpretation of pollen proxies for palaeoclimate reconstitution: The Senegalese “niayes” case-study

The Niayes of Senegal are sahelian interdunal fens, that hosted an azonal subguinean vegetation during the Holocene thanks to the availability of fresh groundwater despite contrasted climatic conditions. Exploratory scenario-based modeling of the zonal hydrogeology has been conducted for different periods with the Cast3M code. The results show that the delay in the onset of humid vegetation ca. 10 ky cal. BP could be ecosystemic and denote a start of the African Humid Period (AHP) ca. 11.5 ky cal. BP. Alternatively, the AHP could have started earlier while its beneficial effects would have been canceled by low sea levels. Vegetation degradation around 7.5 ky cal. BP is shown to have resulted from a climate minoration, that possibly alleviated until 4 ky cal. BP. The rising watertable allowed the degraded forest to persist during that period however. The forest expansion that followed ca. 3.5 ky cal. BP had then clearly a climatic origin. The interpretation of pollens for climate research requires a careful filtering-out of local groundwater availability.     

Last Glacial–Interglacial cycle in the evolution of river valleys in southern and central Poland

The Last Glacial–Interglacial cycle is represented usually by several cuts and fills, which have formed 2–3 terrace steps from the Last Cold Stage and by two or more fills of Lateglacial–Holocene age. Their number depends on the size of the river valley and the position in the longitudinal profile. The sequence of changes reflects shorter stadial–interstadial climatic fluctuations. Generally, aggradation dominates during the cooler phases of the Vistulian and during the Interpleniglacial. The most distinct erosional phases occurred during the change from a more oceanic to a more continental climate before the maximum extension of the ice sheet (25–20 ka BP) and during the Upper Pleniglacial–Lateglacial transition (15–13 ka BP). The second phase coincides with the rapid downcutting in the lower course of the main Vistula valley, which had been blocked earlier by the Scandinavian ice sheet. In the Holocene aggradation prevailed, accelerated by anthropogenic soil erosion. It was only in the mountain foreland that shorter-lived hydrological changes resulted in well expressed several cuts and fills.     

Holocene climate and glacial history of the northeastern Antarctic Peninsula: the marine sedimentary record from a long SHALDRIL core

A high-resolution record of Holocene deglacial and climate history was obtained from a 77 m sediment core from the Firth of Tay, Antarctic Peninsula, as part of the SHALDRIL initiative. This study provides a detailed sedimentological record of Holocene paleoclimate and glacial advance and retreat from the eastern side of the peninsula. A robust chronostratigraphy was derived from thirty-three radiocarbon dates on carbonate material. This chronostratigraphic framework was used to establish the timing of glacial and climate events derived from multiple proxies including: magnetic susceptibility, electric resistivity, porosity, ice-rafted debris content, organic carbon content, nitrogen content, biogenic silica content, and diatom and foraminiferal assemblages. The core bottomed-out in a stiff diamicton interpreted as till. Gravelly and sandy mud above the till is interpreted as proximal glaciomarine sediment that represents decoupling of the glacier from the seafloor circa 9400 cal. yr BP and its subsequent landward retreat. This was approximately 5000 yr later than in the Bransfield Basin and South Shetland Islands, on the western side of the peninsula. The Firth of Tay core site remained in a proximal glaciomarine setting until 8300 cal. yr BP, at which time significant glacial retreat took place. Deposition of diatomaceous glaciomarine sediments after 8300 cal. yr BP indicates that an ice shelf has not existed in the area since this time.The onset of seasonally open marine conditions between 7800 and 6000 cal. yr BP followed the deglacial period and is interpreted as the mid-Holocene Climatic Optimum. Open marine conditions lasted until present, with a minor cooling having occurred between 6000 and 4500 cal. yr BP and a period of minor glacial retreat and/or decreased sea ice coverage between 4500 and 3500 cal. yr BP. Finally, climatic cooling and variable sea ice cover occurred from 3500 cal. yr BP to near present and it is interpreted as being part of the Neoglacial. The onset of the Neoglacial appears to have occurred earlier in the Firth of Tay than on the western side of the Antarctic Peninsula. The Medieval Warm Period and Little Ice Age were not pronounced in the Firth of Tay. The breadth and synchroneity of the rapid regional warming and glacial retreat observed in the Antarctic Peninsula during the last century appear to be unprecedented during the Holocene epoch.     

Late Quaternary seismic stratigraphy and geological development of the south Vøring margin,Norwegian Sea

High-resolution seismic data and sediment cores show that an up to 280 m thick sedimentary sequence has been deposited on the south Vøring margin, off mid-Norway, the last ca 250 ka. The sedimentary succession has been divided into six seismic units, dominated by hemipelagic sediments. Five wedge-shaped massive sequences, of marine isotope stages 8, 6 and 2, interfinger the hemipelagic deposits on the upper slope. The wedge-shaped sequences represent glacigenic debris flows that have been fed by till transported to the shelf edge by grounded ice sheets during maximum glaciations. The hemipelagic units show well-defined depocentres, of various thicknesses, on the upper continental slope. Seismic facies interpretation indicates that the sediment distribution locally has been controlled by currents. Commonly, the hemipelagic units are characterised by parallel and continuous reflectors. However, the second youngest unit identified, deposited between 15.7 and 15.0 ¹⁴C ka BP, is acoustic transparent. We suggest that this unit has been sourced by along-slope transported meltwater plume deposits, released during the initial stage of the last deglaciation of the Norwegian Channel. The hemipelagic sedimentation rates have varied considerably throughout the studied time period. Until ca 21 ¹⁴C ka BP the rates did not exceed 1.4 m/kyr, whereas during the Last Glacial Maximum the rates increased and reached values of about 36 m/kyr before decreasing again at ca 15 ¹⁴C ka BP. Observation of iceberg scourings, of MIS 8 age, about 800 m below the present day sea level, suggest that the south Vøring margin has subsided by a rate of 1.2 m/kyr in the Late Quaternary.     

Holocene glacier and deep water dynamics,Adélie Land region,East Antarctica

This study presents a high-resolution multi-proxy investigation of sediment core MD03-2601 and documents major glacier oscillations and deep water activity during the Holocene in the Adélie Land region, East Antarctica. A comparison with surface ocean conditions reveals synchronous changes of glaciers, sea ice and deep water formation at Milankovitch and sub-Milankovitch time scales. We report (1) a deglaciation of the Adélie Land continental shelf from 11 to 8.5 cal ka BP, which occurred in two phases of effective glacier grounding-line retreat at 10.6 and 9 cal ka BP, associated with active deep water formation; (2) a rapid glacier and sea ice readvance centred around 7.7 cal ka BP; and (3) five rapid expansions of the glacier–sea ice systems, during the Mid to Late Holocene, associated to a long-term increase of deep water formation. At Milankovich time scales, we show that the precessionnal component of insolation at high and low latitudes explains the major trend of the glacier–sea ice–ocean system throughout the Holocene, in the Adélie Land region. In addition, the orbitally-forced seasonality seems to control the coastal deep water formation via the sea ice–ocean coupling, which could lead to opposite patterns between north and south high latitudes during the Mid to Late Holocene. At sub-Milankovitch time scales, there are eight events of glacier–sea ice retreat and expansion that occurred during atmospheric cooling events over East Antarctica. Comparisons of our results with other peri-Antarctic records and model simulations from high southern latitudes may suggest that our interpretation on glacier–sea ice–ocean interactions and their Holocene evolutions reflect a more global Antarctic Holocene pattern.     

Early and middle Holocene in the Aegean Sea: interplay between high and low latitude climate variability

Changes in the orbital parameters, solar output, and ocean circulation are widely considered as main drivers of the Holocene climate. Yet, the interaction between these forcings and the role that they play to produce the pattern of changes observed in different domains of the climate system remain debated. Here, we present new early to middle Holocene season-specific sea surface temperature (SST) and δ¹⁸O_seawater results, based on organic-walled dinoflagellate cyst and planktonic foraminiferal data from two sediment cores located in the central (SL21) and south-eastern (LC21) Aegean Sea (eastern Mediterranean). Today, this region is affected by high to mid latitude climate in winter and tropical/subtropical climate in summer. The reconstructed δ¹⁸O_seawater from LC21 displays a marked (～1.3%) negative shift between 10.7 and 9.7 ka BP, which represents the regional expression of the orbitally driven African monsoon intensification and attendant freshwater flooding into the eastern Mediterranean. A virtually contemporaneous shift, of the same sign and magnitude, is apparent in the δ¹⁸O_speleothem record from Soreq Cave (Northern Israel), an important part of which may therefore reflect a change in the isotopic composition of the moisture source region (Aegean and Levantine Seas). Our SST reconstructions show that Aegean winter SSTs decreased in concert with intensifications of the Siberian High, as reflected in the GISP2 nss [K⁺] record. Specifically, three distinct sea surface cooling events at 10.5, 9.5–9.03 and 8.8–7.8 ka BP in the central Aegean Sea match increases in GISP2 nss [K⁺]. These events also coincide with dry interludes in Indian monsoon, hinting at large (hemispheric) scale teleconnections during the early Holocene on centennial timescales. A prominent short-lived (～150 years) cooling event in core SL21 – centred on 8.2 ka BP – is coeval to the ‘8.2 ka BP event’ in the Greenland δ¹⁸O_ice, which is commonly linked to a melt-water related perturbation of the Atlantic Meridional Overturning Circulation and associated ocean heat transport. By deciphering the phasing between a recently published record of reduced overflow from the Nordic Seas into the northern North Atlantic, the Greenland δ¹⁸O_ice ‘8.2 ka BP event’ anomaly, and the short-lived cooling in SL21, we demonstrate severe far-field impacts of this North Atlantic event in the Aegean Sea. The Aegean is isolated from the North Atlantic oceanic circulation, so that signal transmission must have been of an atmospheric nature.     

Oceanic and atmospheric forcing of early Holocene ice shelf retreat,George VI Ice Shelf,Antarctica Peninsula

We use lake sediment records from an epishelf lake on Alexander Island to provide a detailed picture of the Holocene history of George VI Ice Shelf (GVI-IS). Core analyses included; micropaleontology (diatoms/foraminifera), stable isotope (δ¹⁸O, δ¹³C), geochemistry (total organic carbon (TOC), total nitrogen (TN), C/N ratios) and grain-size analyses. These data provide robust evidence for one period of past ice shelf absence during the early Holocene. The timing of this period has been constrained by 10 AMS ¹⁴C dates performed on mono-specific foraminifera samples. These dates suggest that GVI-IS was absent between c 9600 cal yr BP and c 7730 cal yr BP. This early Holocene collapse immediately followed a period of maximum Holocene warmth that is recorded in some Antarctic ice cores and coincides with an influx of warmer ocean water onto the western Antarctic Peninsula (AP) shelf at c 9000 cal yr BP. The absence of a currently extant ice shelf during this time interval suggests that early Holocene ocean-atmosphere variability in the AP was greater than that measured in recent decades.