EMBRACE-EAR-Growth: Dating ice retreat and advance along the lobate southern margin of the Laurentide Ice Sheet with terrestrial cosmogenic nuclides

The Laurentide Ice Sheet (LIS) covered much of North America ~23,000-years ago, at which time it was similar in size to ice sheets in Antarctica today. Its growth across North America shaped the landscape of the Great Lakes region, which presently host the world’s largest collection of surface freshwater and many unique ecosystems. Additionally, ~34 million people rely on the natural resources in the Great Lakes region to support agricultural, industrial, cultural, and commercial aspects of America’s economy and society.

The LIS started melting in response to increased solar energy at Earth’s poles, and its meltwater flooded across North America to ocean basins where the freshwater disrupted ocean currents and led to hundreds of feet of sea-level rise. Understanding the history of the LIS helps scientists understand potential futures of Earth’s remaining ice sheets and understand feedbacks between ice and Earth’s atmosphere, topography, and oceans.

This study targets the LIS glacial history through the Great Lakes where the LIS operated as numerous lobes of ice. The independent nature of these ice lobes is poorly known because there is very little data on the timing of ice activity here. Through this project, a large dataset of 80 new boulder ice-exposure ages will be collected.

The dated boulders were once covered by lobes of the LIS, and the measured ages reveal when the ice no longer covered the boulder. These ages will be used to reconstruct the melting histories of the Lake Michigan, Saginaw, and Huron Lobes of the LIS. New laboratory facilities will be established at Eastern Michigan University (EMU) – a primarily undergraduate institution serving mostly students from the Great Lakes states.

Dozens of undergraduate students will gain hands-on experience collecting and processing samples for this research, and eight of these students will gain paid research experience under the mentorship of the PI. This project supports the next generation of the STEM workforce through education, research, and knowledge exchange between EMU’s undergraduate students and Earth science graduate students studying at other universities in the Great Lakes region.

The cosmogenic isotope, 10Be, is the most common geochronometer used to date exposure ages of glacial erratics. The currently sparse extent of geochronological data in the Great Lakes restricts our understanding Laurentide Ice Sheet (LIS) retreat, meltwater routing to ocean basins, and our ability to link LIS retreat to specific large-scale climatic events (i.e.

Heinrich or Dansgaard-Oeschger events). This project will produce 80 new 10Be-based ages of ice retreat for >7 moraines across the region, and results will be used to (1) constrain the timing of retreat and advance for independently operating lobes of the LIS, (2) draw chronological relationships between LIS ice activity in the Great Lakes region to its better-dated margins along the Atlantic seaboard, and (3) produce a new dataset that may complement and/or sharpen existing 14C-based patterns of LIS retreat.

This EMBRACE award increases participation of the next diverse generation of Geoscientists at EMU in the following ways: enhanced access to geoscience courses by reducing enrollment barriers for courses Great Lakes glacial content; mentorship of eight Geoscience students through paid research experiences (compensation is crucial because students may not otherwise afford to participate in unpaid research); development of laboratory spaces at EMU that will benefit all Geoscience faculty and students beyond the length of this award; and growth of a stronger Geosciences workforce for the Great Lakes by facilitating peer-to-peer knowledge and experience exchanges through the Great Lakes Earth Exchange speaker series.

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.