Depositional and circulation changes at the Chukchi margin, Arctic Ocean, during the last two glacial cycles

报告简介:

The shallow Chukchi-East Siberian margin of the Arctic Ocean was repeatedly impacted by Pleistocene glaciations and related changes in sea level and circulation. The depositional history across the last two Arctic glacial cycles is investigated in sediment core ARC6-C15 from the foot of the Chukchi Rise, an extension of the Chukchi Sea shelf that was impacted by the East Siberian Ice Sheet (ESIS). Our proxy data indicate a large extent of the ESIS, likely blocking the westward sediment transport from the Laurentide Ice Sheet (LIS) during the penultimate glaciation estimated to have occurred within an age span from Marine Isotope Stage (MIS) 4 to 6. The deglacial environments are characterized by enhanced sediment inputs from the East Siberian and Chukchi shelves, while overlying interstadial/interglacial sediments have a signature of the Chukchi Sea and the Beaufort Gyre. During the last glaciation, the ESIS had a smaller impact on the Chukchi margin, and the deglaciation was dominated by the LIS sediment sources. Glacial discharge from the Mackenzie area is identified in the Bølling/Allerød interval, while later deglacial pulses can be tracked to the Canadian Arctic Archipelago. In addition to glacigenic sediment inputs, both deglacial intervals contain Fe-Mn micronodules, possibly formed under the influence of meltwater pulses during sea level rise. An increase in the chlorite content that likely marks the flooding of the Bering Strait is identified at the start of the Holocene. A pronounced oxygen and carbon isotope excursion in the early Holocene may indicate hydrographic changes in the Arctic Ocean related to the 8.2 ka meltwater discharge event.

报告人简介:

肖文申
Associate Professor Wenshen Xiao works at the State Key Laboratory of Marine Geology, Tongji University. By using a variety of tools, such as microfossils, sedimentological and geochemical proxies, his research focuses on paleoenvironment changes in polar regions at different time scales. He has participated in multiple scientific expeditions to the Arctic Ocean and the Southern Ocean. His research interests include (1) evolution of ice sheets and circulation changes in the Arctic and Antarctic regions; (2) changes in surface water (temperature, sea ice, productivity, meltwater etc.) and bottom water (temperature, ventilation etc.) conditions in the polar/subpolar regions; (3) Arctic/Antarctic sediment stratigraphy; (4) climatic connections between polar and low latitude areas.