Collaborative Research: Testing Laurentide Ice Sheet Climate Response and Younger Dryas Trigger with Glacial Varves

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This project has two objectives. 1) Document the response of the former ice sheet that covered the North American mid-continent to rapid climate changes that occurred at the end of the last ice age. Such a record enhances our ability to predict the response of ice sheets to modern climate change. 2) Test the role of increased freshwater influx to the Atlantic Ocean as a possible trigger for these rapid climate changes, specifically the cold interval known as the Younger Dryas. Modern freshening in the North Atlantic and Arctic Oceans has raised concerns that global warming driven increases in glacier runoff could trigger climate cooling. To evaluate models that use this event to assess the future response of the Atlantic Ocean to predicted freshening, the connections (if any) between freshwater discharge and routing before and during the Younger Dryas need to be resolved.The primary records that will be generated are varve thickness datasets from a large glacial lake, proximal to the former ice sheet. Glacial varves are yearly sediment couplets that appear similar to tree rings, and as such provide an annually resolvable record of how climate affected the ice sheet. The varves will be recovered by coring sediments from many lakes, spanning a broad region west of Lake Superior. By matching thickness patterns between all sites, a 5000+ year time series is anticipated. Working in collaboration with staff at Voyageurs National Park (Minnesota), this work will be showcased for the general public via a permanent indoor exhibit on varves as records of climate and environmental change.