Collaborative Research: NSF/GEO-NERC: The Collapse of the Cordilleran Ice Sheet: Using Glacial Dipsticks to Constrain Ice Sheet Modeling

Boston College, Chestnut Hill MA

Investigators

Abstract

This project will determine when and how quickly the Cordilleran Ice Sheet in western Canada disappeared since the end of the last ice age, approximately 20 to 10 thousand years ago. It will create a 3-D reconstruction of the ice sheet’s collapse through geologic dating of rock samples collected from mountains across the region that record the lowering ice sheet surface and use computer models of the ice sheet shape to help ‘connect the dots’ between these datapoints. Because the Cordilleran Ice Sheet shared many similarities with the present-day Greenland Ice Sheet, this reconstruction will provide a key test for models used to simulate Greenland’s future decay – one of the largest and most uncertain sources of sea level rise. The project will build an international collaboration from the U.S., U.K., and Canada and train the next generation of scientists in holistic approaches to better understanding how ice sheets collapse. The team will contribute content to a popular website on glaciers targeted at the general public and teachers/students. A climate journalist will take part in fieldwork and potentially write a story. Projections of future sea level rise rely on ice sheet models that are highly tuned to the present day, limiting confidence in their ability to simulate the future. Recent advances in cosmogenic dating as well as ice sheet modeling and uncertainty quantification now make it feasible to use reconstructions of past ice sheet changes to test and improve coupled climate-ice sheet models. The deglaciation of the Cordilleran Ice Sheet is poorly constrained, yet this ice sheet offers great potential to constrain models due to its similarities to the southern Greenland Ice Sheet: mountainous, high mass accumulation, strong precipitation gradients, and marine/land terminating. The Cordilleran Ice Sheet is also thought to have played a key role in rapid sea level and climate changes during the last deglaciation, but evidence of this is limited. This project will produce the first 3-D reconstruction of Cordilleran Ice Sheet collapse. It will apply the "glacial dipstick" approach, generating 135 10Be ages along ~15 vertical transects. Using a Bayesian Uncertainty Quantification approach, these field data will be combined with Cordilleran Ice Sheet simulations from a complex yet efficient coupled climate-ice sheet model used for future projections. This will produce an ensemble of plausible reconstructions for the deglaciation of the Cordilleran Ice Sheet. 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.