ALBERT

Description: The Northeast Greenland continental shelf became one of the tipping elements in our climate system. Ongoing mass loss of the Greenland Ice Sheet, intensive sea-ice loss, the influence of warm, recirculating Atlantic Water towards the inner shelf, intensive bottom-melting at the underside of local marine-terminating outlet glaciers, glacier retreat and ice-sheet disintegration plays a fundamental role in terms of ongoing anthropogenic warming. Marine sediment Core PS100/270 was recovered aboard the RV Polarstern cruise PS100 in 2016 directly in front of 79NG on the inner NEG continental shelf (79°29.83'N, 18°8.40'W) in a water depth of 424 m. Chronology of the 9.51 m long Core PS100/270 is based on 13 AMS 14C ages, measured on benthic foraminifera. Sediment samples of Core PS100/270 were investigated to analyse microfossil assemblages, biomarker and bulk parameter proxy data. Additionally, the lithology, x-ray radiographs and geophysical properties (wet bulk density and magnetic susceptibility) were considered to perform a direct comparison with other records nearby e.g. PS2623. Four distinct lithofacies units were identified within this sedimentary record and are based on the, x-ray, lithology and biomarker data: stiff, overconsolidated diamiction; an indistinct/irregular laminated silty clay; a laminated silty clay and silty clay. Gravity Core PS100/270 was selected and studied in detail to reconstruct past sea-ice formation and ice-sheet dynamics, terrigenous input, primary productivity and the influence of warm, recirculating Atlantic Water on the shelf during the late Weichselian deglacial to late Holocene. The new high-resolution records presented here from the Northeast Greenland continental shelf provide helpful information about the pace of small- and large-scale climate variations, form the basis to improve future climate predictions and might serve as suitable analogue to ongoing anthropogenic warming by covering warmer periods in the past e.g. early Holocene Thermal Maximum.

Description: A biomarker approach is applied on a well-dated core from the Beaufort Sea directly off the Mackenzie River to reconstruct changes in sea ice, sea surface temperature (SST), primary productivity, and terrigenous input. High-resolution records indicate that the southern Beaufort Sea was nearly ice-free in summer during the last deglaciation and early Holocene, and a seasonal sea-ice cover developed during the mid-late Holocene, coinciding with a drop in terrigenous sediment flux and primary production. Superimposed to this climate-driven long-term change in surface-water characteristics, we document two major flood events during the deglacial to Holocene transition. Such major flood events in the Beaufort Sea region may have profound effect on global climate change, especially during times when the massive Laurentide Ice Sheet (LIS) collapsed, and huge amount of freshwater was drained into the Beaufort Sea. This freshening of the Arctic Ocean may have resulted in increased freshwater export into the North Atlantic, causing reduced North Atlantic deep-water formation. The first flood event occurring at ca. 13 kyr BP is related to the Younger Dryas (YD) flood which may have caused severe cooling. The second flood event occurred at ca. 11 kyr BP, whose existence has been hypothesized for a long time but restricted by quality records. Through studies of our sediment core and other records nearby, we hypothesize that the second flood event is more related to shelf flooding induced by strong coastal erosion.