Changes in sediment provenance and ocean circulation on the northern slope of the Bering Sea since the last deglaciation

Abstract

Changes in water circulation in the Bering Sea have profoundly impacted biological productivity, carbon cycle and global ocean circulation, especially from the last deglaciation to the Holocene. Grain size and clay mineral composition were investigated in core ARC6-B10, collected from the northern Bering slope, in order to reveal changes in circulation and sediment provenance since the late deglaciation (~13.7 ka). The results highlight changes in sea level and atmospheric circulation as the primary controls on the variations in grain size and clay mineralogy. Deglacial sea level rise deepened the water passages along the Aleutian Arc, enhanced the inflow of North Pacific water that strengthened the circulation of the Bering Sea, and receded the coastline. These changes increased the supply of smectite-enriched sediments from the Aleutian Islands to the core site. A temporary reduction in smectite and an increase in the illite and chlorite contents during the Preboreal period correspond to the opening of the Bering Strait; this is attributed to rapid sea level rise which resulted in increased sediment resuspension from the shelf. During the mid- to late Holocene, when the sea level stabilized, changes in the Aleutian Low (AL) were a major factor modulating changes in ocean circulation. A weakened AL in the mid-Holocene intensified the northward Bering Slope Current and the increased the flow through the Bering Strait, while an intensified AL, along with an expanded sea ice cover during the late Holocene may have weakened the northward flow.