Cosmogenic surface exposure dating of Cordilleran-Laurentide ice-sheet separation during the last deglaciation: implications for abrupt sea-level rise

Oregon State University, Corvallis OR

Investigators

Abstract

The rise in sea level during the last deglaciation (21,000-6,000 years ago) was punctuated by intervals of abrupt sea-level rise, called meltwater pulses (MWP), which indicate the development of instability in one or more of Earth's ice sheets. The largest MWP, MWP-1A, occurred 14,600-14,300 years ago with ~14 m of global-mean sea-level rise. It was recently hypothesized that the collapse of an ice saddle between the Cordilleran (CIS) and Laurentide (LIS) ice sheets could have caused MWP-1A when the two ice sheets separated. Results from this research will provide important data on whether the ice sheet failure caused rapid jumps in sea level. Determining if the ice sheet separation caused a MWP will provide insight into the evolution of North Atlantic climate and its relationship to meltwater discharge to the Arctic Ocean where much of the ice sheet separation meltwater would be routed. These findings will also have implications for development of instability in the Greenland ice sheet as it has an ice saddle similar to the one previously seen in the Cordilleran-Laurentide. Finally, these results will date when an ice-free corridor formed between the Cordilleran and Laurentide ice sheets, which has important ramifications for human migration routes to the Americas. This project will date the end of CIS-LIS separation with 50 boulder cosmogenic surface exposure ages at six locations along the suture zone of the ice sheets between 50°N and 60°N. These ages will determine when CIS-LIS separation was complete, and if it was concurrent with MWP-1A or another interval of rapid sea-level rise. They will also document if CIS-LIS separation occur over centuries, which could cause a MWP, or over millennia which would be inconsistent with separation causing a MWP.