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Coastal bathtub rings: What ancient shorelines tell us about future sea level rise

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Wedgewood Resort Borealis Ballroom

Julie Brigham-Grette
University of Massachusetts-Amherst

Glacial and interglacial change during the ice ages uniquely imposed on the Bering Strait region some of the most radical changes in sea level and paleogeography documented in the Northern Hemisphere. The Bering Land Bridge is a landscape that existed because of glaciation, exposing the shallow parts of the Bering and Chukchi seas.  Following the transition from a forested Arctic 3 million years ago to the first major glaciation of the northern hemisphere about 2.6 million years ago, coastal marine deposits found along the coasts of Alaska and Chukotka record a number of critical transitions in the evolution of Northern Hemisphere climate.  Ancient shorelines, or bathrub rings, record not only natural global warming but also the northward migration of marine ecosystems and changes in the extent of sea ice along Alaska’s shores. Changes in Beringian shorelines likely influenced the migration of man into North America. New research helps us understand the rate and timing of the last submergence of the Bering Strait, 12,000 years ago, and how ongoing sea level rise will likely cause changes in the shorelines we live along today.