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Abstract: We present evidence for freshwater forcing from the Greenland Ice Sheet during the last deglaciation, explore its potential involvement in the Younger Dryas cooling, and investigate the role of Atlantic Intermediate Water in the retreat of the Greenland Ice Sheet. Paleoceanographic conditions and ice-sheet retreat history are interpreted from IRD, stable isotopes and foraminiferal assemblages in sediment cores retrieved along the length of the Kangerlussuaq Trough, a cross-shelf trough on the southeast Greenland shelf. The Vedde Ash (11,980±cal.yr BP), which is a marker bed within the Younger Dryas, and the Saksunarvatn tephra (10,180±cal.yr BP) an early Holocene marker horizon, have been located in these cores. The tephra markers and calibrated 14C dates on foraminifers and molluscs provide the basis for the age models in the cores. The stable isotope records indicate a 0.5‰ depletion of the 18O between 13.4 and 12.8calka BP. A pronounced light isotope event, exceeding 1.5‰ on the inner shelf and 0.8‰ on the outer shelf, occurs at the beginning of the Younger Dryas Cold period (12.8cal.ka BP) and ends by 12calka BP, immediately before deposition of the Vedde Ash. The light isotope spikes are interpreted as glacial meltwater spikes associated with retreat of the adjacent Greenland Ice Sheet. Associated with the light isotope events are episodic high percentages of the Atlantic Intermediate Water benthic foraminiferal species, Cassidulina neoteretis, which continue from the Bølling/Allerød into the Younger Dryas. High percentages of this species suggest that Atlantic Intermediate Water entered the Kangerlussuaq Trough during the Allerød and the Younger Dryas via the Irminger Current, as it does today. We conclude that advection of Atlantic Intermediate Water into the Kangerlussuaq Trough, south of the Denmark Strait, promoted melting and retreat of the marine portions of the Greenland Ice Sheet, explaining the observed glacial meltwater spikes. [Copyright &y& Elsevier]

Abstract: The Late Weichselian–Early Holocene variability of the North Atlantic Current has been studied with focus on the zonal component of this meridional transport during the transition from glacial to interglacial conditions. The investigated sediment core is from 409 m water depth in the SW Barents Sea. Eight Accelerator mass spectrometry (AMS) 14C dates show that the core covers the last 20,000 cal yr B.P. with a centennial scale resolution during Late Weichselian–Early Holocene. Planktic foraminiferal assemblages were analyzed using the >100 μm size fraction and foraminiferal planktic and benthic δ13C and δ18O isotopes were measured. Furthermore, a range of physical and chemical analyses has been carried out on the bulk sediment samples. Four time periods have been identified which represent the varying oceanographic conditions in Ingøydjupet, a glacial trough located off the north coast of Norway in the SW Barents Sea. 1) The late glacial (before ca 15,000 cal yr B.P.) influenced by the nearby ice sheets with high amounts of sea ice- or iceberg-transported detritus. 2) The late Oldest Dryas stadial and the Bølling-Allerød interstadial (ca 15,000–12,700 cal yr B.P.) with cold surface water conditions influenced by the collapse of the nearby ice sheets, high amounts of sea ice- or iceberg-transported detritus and melt water and weak subsurface inflow of Atlantic Water. 3) The Younger Dryas cold stadial (12,700–11,650 cal yr B.P.) with low primary productivity and extensive sea ice cover and 4) The Preboreal and Early Holocene (11,650–6800 cal yr B.P. cal yr B.P.) with strong influx of Atlantic Water into the area, near absence of ice rafted debris and generally ameliorated conditions in both surface and bottom water masses as seen from a high flux of foraminifera and increased marine primary production. [Copyright &y& Elsevier]

Abstract: A sediment core from the Lofoten Contourite Drift on the continental slope off Northern Norway, proximal to the former Vestfjorden–Trænadjupet Ice Stream, details the development, variability and decline of marine margins of the northwestern Fennoscandian Ice Sheet during the time interval 25.3–14calkaBP, including the Last Glacial Maximum and onset of the deglaciation based on high-resolution IRD records. From the core interval between 25.3 and 17.7calkaBP we report data points with a mean time step of 10 years, between 17.7calkaBP and the Holocene time steps are typically 50 years. The core is divided into 7 informal ice-rafted debris (IRD) zones based on the variations in IRD including 7 major IRD maxima (A–G), inferred to represent periods of high iceberg production. Petrological identification reveals dominance of crystalline IRD (monocrystalline, plutonic and metamorphic rock fragments) accounting for 75–80% of total IRD assemblages, while sedimentary fragments generally account for 15–20%. The crystalline fragments (including eclogite and mangerite from a nearby terrestrial source) increase across the IRD peaks while the sedimentary fragments remain constant. This points to the importance of erosional products from icebergs originating from fast-flowing paleo-ice streams including the Vestfjorden–Trænadjupet Ice Stream draining from the Fennoscandian mainland during the IRD maxima periods. Increased temperature of the adjacent surface water masses was probably an important external forcing factor on the Fennoscandian Ice Sheet behavior because some IRD maxima and plumite deposition from meltwater plumes post-date periods of increased sea surface temperatures. The peak IRD depositions occur in centennial and millennial time cycles (∼200, 1030 and 3900 year) indicating some external forcing by solar variation. Both mechanisms could explain the observed synchronous instability of the northwestern Fennoscandian Ice Sheet to other European Ice Sheets. [Copyright &y& Elsevier]

The paleoceanographic development of the eastern Fram Strait during the transition from the cold Late Glacial and into the warm Early Holocene was elucidated via a multiproxy study of a marine sediment record retrieved at the western Svalbard slope. The multiproxy study includes analyses of planktic foraminiferal fauna, bulk sediment grain size and CaCO3 content in addition to Mg/Ca ratios and stable isotopes (δ13C and δ18O) measured on the planktic foraminifer Neogloboquadrina pachyderma. Furthermore paleosubsurface water temperatures were reconstructed via Mg/Ca ratios (sSSTMg/Ca) and transfer functions (sSSTTransfer) enabling comparison between the two proxies within a single record. The age model was constrained by four accelerator mass spectrometry (AMS) 14C dates. From 14,000 to 10,300 cal yr B.P. N. pachyderma dominated the planktic fauna and cold polar sea surface conditions existed. The period was characterized by extensive sea ice cover, iceberg transport and low subsea surface temperatures (sSSTTransfer ~ 2.1 °C; sSSTMg/Ca ~ 3.5 °C) resulting in restricted primary production. Atlantic Water inflow was reduced compared to the present-day and likely existed as a subsurface current. At ca. 10,300 cal yr B.P. Atlantic Water inflow increased and the Arctic Front retreated north-westward resulting in increased primary productivity, higher foraminiferal fluxes and a reduction in sea ice cover and iceberg transport. The fauna rapidly became dominated by the subpolar planktic foraminifer Turborotalita quinqueloba and summer sSSTTransfer increased by ~ 3.5 °C. Concurrently, the sSSTMg/Ca recorded by N. pachyderma rose only ~ 0.5 °C. From ca. 10,300 to 8600 cal yr B.P. the average sSSTMg/Ca and sSSTTransfer were ~ 4.0 °C and ~ 5.5 °C, respectively. The relatively modest change in sSSTMg/Ca compared to sSSTTransfer can probably be tied to a change of the main habitat depth and/or shift in the calcification season for N. pachyderma during this period. [ABSTRACT FROM AUTHOR]