Geological constraints on the disappearance of the Laurentide Ice Sheet

Project Description

Knowledge of past warm periods and their effect on the cryosphere can help place modern warming and glacier demise in a longer-term context. LIS is Earth's most dynamic ice sheet having undergone repeated continental-scale expansions and contractions through the Quaternary. Evidence for past ice-sheet maxima is found in terrestrial and marine settings, yet the minimum extent of the LIS during interglaciations is largely unknown. The Barnes Ice Cap, the last remaining vestige of LIS, once covered much of the North American continent during the Last Glacial Maximum (~27-20 ka). The investigators will measure multiple cosmogenic nuclides (Beryllium-10, Carbon-14, Neon-21, Aluminum-26, and Chlorine-36) from recently exposed bedrock along the Barnes Ice Cap to quantify how frequently and for how long the LIS/Barnes Ice Cap achieves its modern dimensions during interglaciations. They will use a new field method that relies on shallow bedrock cores (rather than surface samples), which will be combined with the inventory of multiple cosmogenic nuclides with different half-lives, to quantify total Quaternary exposure and burial durations of bedrock surfaces just now being exposed by receding ice. Results will be compared to recent cosmogenic nuclide measurements from beneath the Greenland Ice Sheet Project 2 (GISP2) borehole that suggest the Greenland Ice Sheet nearly completely deglaciated on several occasions through the Quaternary.

This project has been supported by funding from: