Sedimentology, organic geochemistry, and stable isotopes of core PS2138-1

We studied variations in terrigenous (TOM) and marine organic matter (MOM) input in a sediment core on the northern Barents Sea margin over the last 30 ka. Using a multiproxy approach, we reconstructed processes controlling organic carbon deposition and investigated their paleoceanographic significance in the North Atlantic-Arctic Gateways. Variations in paleo-surface-water productivity are not documented in amount and composition of organic carbon. The highest level of MOM was deposited during 25-23 ka as a result of scavenging on fine-grained, reworked, and TOM-rich material released by the retreating Svalbard/Barents Sea ice sheet during the late Weichselian. A second peak of MOM is preserved because of sorptive protection by detrital and terrigenous organic matter, higher surface-water productivity due to permanent intrusion of Atlantic water, and high suspension load release by melting sea ice during 15.9-11.2 ka.

(Table 1) Stable oxygen isotopic ratios and yearly snow accumulation of firn and ice cores from Svalbard

We analyse ice cores from Vestfonna ice cap (Nordaustlandet, Svalbard). Oxygen isotopic measurements were made on three firn cores (6.0, 11.0 and 15.5 m deep) from the two highest summits of the glacier located on the SW-NE and NW-SE central ridges. Sub-annual d18O cycles were preserved and could be counted visually in the uppermost parts of the cores, but deeper layers were affected by post-depositional smoothing. A pronounced d18O minimum was found near the bottom of the three cores. We consider candidates for this d18O signal to be a valuable reference horizon since it is also seen elsewhere in Nordaustlandet. We attribute it to isotopically depleted snow precipitation, which NCEP/NCAR reanalysis shows was unusual for Vestfonna, and came from northerly air during the cold winter of 1994/95. Finding the 1994/95 time marker allows establishment of a precise depth/age scale for the three cores. The derived annual accumulation rates indirectly fill a geographical gap in mass balance measurements and thus provide information on spatial and temporal variability of precipitation over the glacier for the period spanned by the cores (1992-2009). Comparing records at the two locations also reveals that the snow net accumulation at the easternmost part of Vestfonna was only half of that in the western part over the last 17 years.