BERING STRAIT SEA LEVEL DETECTS THE TIMING AND GEOMETRY OF NORTH AMERICAN ICE SHEET MELT (Invited Presentation)

During the Last Glacial Maximum, continental ice sheets lowered globally averaged sea level ~130 m, exposing the Bering Strait land bridge. During the subsequent deglaciation, sea level rose rapidly and ultimately flooded the Bering Strait, linking the Arctic and Pacific Oceans. Observational records of the Bering Strait flooding have suggested two apparently contradictory scenarios for the timing of the reconnection; according to sediment core records, flooding occurred at 11.5 ka, whereas species dispersal data suggest a connection by 13 ka. We reconcile these enigmatic datasets using gravitationally self-consistent sea-level simulations that vary the timing and geometry of ice retreat between the Laurentide and Cordilleran Ice Sheets to the southeast of the Bering Strait to fit observations of a two-phased flooding of the Bering Strait continental shelf. Assuming the datasets are robust, we demonstrate that their reconciliation requires a substantial melting of the Cordilleran and western Laurentide Ice Sheet from 13,000 to 11,500 years ago. This timing provides a freshwater source to the Arctic Ocean for the widely debated Younger Dryas cold episode (12,900 to 11,700 years ago).

We next explore how the timing of North American ice saddle melt modulates the stability of the fast-flowing marine-terminating Amundsen Ice Stream, which was located in the Northwestern Laurentide Ice Sheet. Finally, we outline future directions for reconstructing the details of Bering Strait flooding, with implications for bounding global and regional ice sheet histories over the last glacial cycle.