Millennial‐scale climate change and intermediate water circulation in the Bering Sea from 90 ka: A high‐resolution record from IODP Site U1340

Abstract

Millennial‐scale climate events in the North Pacific are thought to be related to changes in the circulation of North Pacific Intermediate Water, which may have formed in the Bering Sea in the past. To advance our understanding of the mechanisms that underlie millennial‐scale events, Bering Sea sediment cores from the Integrated Ocean Drilling Program site U1340 were used to construct high‐resolution, multiproxy climate records of the last 90,000 years. Sediment density records show millennial‐scale events resembling Dansgaard‐Oeschger events, several of which are laminated. Interstadials were characterized by 3–5 °C warming, increased productivity driven by upwelling, and reduced benthic oxygenation. Bering Sea intermediate water also changed over longer timescales; our records show the presence of intermediate water with lower salinity and higher oxygen content than modern beginning around 60 ka and persisting until the beginning of the deglaciation. The Bølling‐Allerød was characterized by high productivity, laminated sediments, and strong denitrification signature. Our data support the idea that productivity‐derived changes in oxygenation at intermediate water source regions may have contributed to the intensification of the North Pacific–wide oxygen minima during the Bølling‐Allerød.