NOAA/WDS Paleoclimatology - Bering Sea Diatom, Carbon, Nitrogen and Stable Isotope Data from Marine Isotope Stage 11 (430-368 ka)

The extreme warmth of Marine Isotope Stage (MIS) 11 has been extensively studied in the terrestrial realm; however, much less is known about its expression in the North Pacific. Here, we present a multi-proxy record using sedimentology, diatoms, and organic geochemistry to reconstruct sea ice and primary productivity from MIS 12 to 10 (430-368 ka) from Integrated Ocean Drilling Program (IODP) Site U1339 in the southeastern Bering Sea (Umnak Plateau). MIS 12 is characterized by extensive seasonal sea ice, which declines during deglaciation, but does not remain low throughout MIS 11. Instead, diatoms and ice-rafted debris indicate that ice re-advanced across the plateau during the interglacial climatic optimum. In contrast, sea ice is not present at the Umnak Plateau today. During MIS 11, sea ice at the Umnak Plateau may have persisted due to a more easterly and/or weaker Aleutian Low. Laminated sediments at the boundary between MIS 12 and 11 point toward enhanced seasonal productivity during deglaciation. However, productivity does not remain high once the interglacial stabilizes. The gradual decline in productivity over the course of MIS 11 occurs independently of fluctuations in sea ice and upwelling, and instead may be a response to increasing nutrient limitation.