PEAK WARMING DURING MARINE ISOTOPE STAGE 11 IN THE ARCTIC OCEAN BASED ON PLANKTIC FORAMINIFERA

Marine Isotope Stage (MIS) 11, ~424-374 ka, is characterized globally by warm sea-surface temperatures (SSTs), high sea level, and atmospheric carbon dioxide (CO₂) concentrations comparable to those of the pre-industrial period. MIS 11 therefore acts as an important indicator of future oceanic conditions as the average global temperature continues to increase. We studied the paleoceanography of MIS 11 in the Arctic Ocean, including the preceding glacial MIS 12, the MIS 12-11 transition (Termination V), and the MIS 10 transition using piston cores from the Northwind, Mendeleev, and Alpha Ridges. Chronology was based on δ¹⁸O stratigraphy, biostratigraphy, and tuning various physical and biological features to the Lisiecki and Raymo d¹⁸O (LR04) curve and astronomical timescale. We used planktic foraminifer assemblages, including the species Turborotalita egelida, a subpolar species that dominates during MIS 11, to estimate SSTs via modified transfer functions. There are few ways to reconstruct the paleo-sea ice extent in the Arctic Ocean as proxies like δ¹⁸O are limited to recording water average temperature and salinity. Planktic foraminifera such as T. egelida and Neogloboquadrina pachyderma can be used as proxies for SSTs and sea ice cover as they live at ~80 m water depth and are directly affected by surface water conditions. In comparing the MIS 11 assemblages to those of the modern (MIS 1 and Holocene, as found in the top 0-1 cm of oceanic sediment), we can infer that MIS 11 SSTs ranged between 5-10°C and that the Arctic Ocean experienced seasonally sea-ice free conditions, similar to today.