Collaborative Research: Geological constraints on the disappearance of the Laurentide Ice Sheet

The Laurentide Ice Sheet (LIS) once covered much of the North American continent. It grows and expands during cold periods and contracts during warm periods in Earth's recent geological past. Today, the last remaining vestige of the LIS is the Barnes Ice Cap, located on central Baffin Island. While tracking the size of the LIS at times when it was significantly larger than today is relatively straightforward, constraining the size and frequency of LIS minima is much more challenging but can provide a long-term context in which to evaluate the current small state of the Barnes Ice Cap. For this project, the investigators will use new, cutting-edge geological techniques to piece together how often the LIS reaches its current dimensions. The team will be led by an early-career Hispanic geoscientist, and the project will train one doctoral and two undergraduate student. The investigators will participate in institutional open houses that are available to the public and recruit undergraduate student participation through institutional internship programs.

Knowledge of past warm periods and their effect on the cryopshere 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 award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.