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Cosmogenic surface exposure dating of Arctic NW Laurentide ice-sheet deglaciation: implications for abrupt climate change


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The objective of this project is to date the retreat of the Keewatin Dome of the Arctic NW Laurentide ice sheet (LIS) during the last deglaciation and test the relationship among the timing and rate of ice retreat, discharge of meltwater to the Arctic Ocean, and abrupt climate change. The study will also document how meltwater associated with Arctic NW LIS retreat may have contributed to deglacial sea level rise. The investigator will measure the cosmogenic nuclide beryllium-10 from 80 boulders at 11 sites along a 1000 km east-west transect. The project will support two undergraduate students who will be trained in glacial geology, geochronology, paleoclimatology, and Arctic fieldwork. Public outreach is planned for Da Vinci Days and a farmers' market in Corvallis, Oregon, as well as to northern communities and local geoscientists through the annual Yellowknife Geoscience Forum. This project will provide new understanding of the relationship among Arctic ice-sheet retreat, Atlantic meridional overturning circulation, and climate change. Retreat of the Arctic NW Laurentide ice sheet (LIS) will be dated using beryllium-10 surface exposure ages for more than 80 boulders at 11 sites along a 1000 km long transect perpendicular to LIS retreat at 65 degrees North. Sampling density will be 100 km, resolvable by ice sheet models. The investigator will address two primary questions: 1) What are the spatiotemporal patterns of Arctic NW LIS deglaciation and was retreat monotonic or were their periods of accelerated retreat? And 2) Do Arctic NW LIS retreat-rate changes correspond with deglacial periods of Northern Hemisphere abrupt climate change, such as the Younger Dryas? The first question will be answered using beryllium ages, with the sampling approach able to resolve century-scale changes in ice-margin retreat. The second question will be addressed by comparing the timing of Arctic NW LIS retreat at the 11 sampling locations to abrupt climate events of the last deglaciation. To convert the ice-margin retreat record into changes in ice volume and meltwater discharge, the investigator will use the chronology to filter Bayesian deglacial LIS-model simulations, which will force sea-level/earth models and be compared to deglacial climate simulations.