SHELF SEDIMENTATION PATTERNS IN ARCTIC SIBERIA SINCE THE LAST GLACIAL MAXIMUM

Radiocarbon-dated (AMS) sediment cores from the Laptev Sea shelf can provide annual to centennial resolution insight into records of land-shelf-ocean interaction during the Holocene. Modern environmental processes in this polar region are determined by strong seasonal as well as interannual to decadal variability in sea-ice cover and riverine freshwater discharge. Variations in both, high-latitude freshwater budget and spatial sea ice distribution, are regarded crucial climate factors.

Using sediment cores from different water depths, micropaleontological, sedimentological, and geochemical approaches have proven to be sensitive tools to reconstruct not only the postglacial inundation history, but also to identify climate-driven environmental change on arctic shelves. Stable carbon isotope data of organic matter in marine sediments are used to reconstruct the terrestrial fluvial input during the Holocene and to support the general chronology. In comparison with other proxy methods, such as certain mineral phases, the history of land-to-ocean connection on the western shelf shows a rather cyclic nature of terrestrial sediment input since about 16 ka. This part of the shelf is directely linked to the Siberian basaltic province in the hinterland through rivers. A dominant cyclicity of the Holocene river input is also found on the eastern shelf, within paleosalinity reconstructions based on diatoms and benthic foraminiferal oxygen isotopes. While the early Holocene records until about 7 ka reflect depositional changes primarily caused by the postglacial transgression, variable sea-ice conditions and surface salinities with a periodicity of 1000-1500 years existed during the later Holocene. A pronounced temporal pattern is also recognized in proxy data reflecting the sea-ice drift patterns in this area. As this pattern is time-coherent with other records from the North Atlantic region, it seems evident that environmental processes on the Siberian shelves are forced by northern hemisphere changes in atmospheric circulation regimes.