Collaborative Research: 3 Myr of Laurentide Ice Sheet History Inferred from Cosmogenic Nuclides in Ice-Rafted Debris

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The Laurentide Ice Sheet over North America caused large changes in climate and sea level as it grew and shrank over ice age cycles during the past three million years, but little is known about the ice sheet’s detailed history throughout this interval. This project will determine how big the ice sheet was through time using chemical markers in layers of sand on the seafloor that melted out of icebergs drifting from North America. This method provides a new way to learn about past changes in the Laurentide Ice Sheet and test ideas for how climate change and ice sheets affect each other. The results should help with predictions of sea-level rise far into the future due to global warming and melting polar ice sheets. This project will also educate and involve a wide range of people in climate science in several ways. Videos about the research will be sent to Boston Public Schools through the BoSTEM organization to help students in the area learn about careers in science. The researchers will participate in activities through the McAuliffe Center for Integrated Science Learning at Framingham State University to teach middle and high school students and teachers about climate change. College students will help with the research during summers through the Integrated Science for Society NSF Research Experience for Undergraduates at Boston College, which tries to find students from underrepresented minority groups or who are the first in their family to go to college and that do not have research possibilities at their school. Lastly, the project will support a female Ph.D. student already at Boston College and an M.S. student at the University of Vermont. The Laurentide Ice Sheet over North America was one of the largest drivers of climate and sea level over the ice age cycles of the past three million years, but its history over this interval is shrouded in uncertainty largely due to limitations of conventional geologic records. This project will take a new approach, measuring the concentrations of rare chemicals in quartz sand layers from ocean sediment cores that melted out of drifting North American icebergs. The chemistry of the sand reflects the history of North American ice sheet cover because the chemicals accumulate in land surfaces exposed to the atmosphere but radioactively decay away when the surfaces are buried by ice. Four sediment cores will be analyzed to reconstruct long-term Laurentide Ice Sheet evolution, and analyses of sand samples collected across eastern Canada will show how their chemistry records ice sheet variations over the most recent ice age cycle. Together with similar reconstructions produced over the past five years from Greenland and Antarctica, these records will provide a comprehensive picture of how these three ice sheets varied in the past and contributed to global sea level. The results will offer much-needed constraints to test theories and models of paleo-ice sheet change, useful for improving long-term future projections of ice sheets on Earth today. This project will increase literacy and diversity in climate science in multiple ways. “Science Bites” videos about the research will be distributed to Boston Public Schools through BoSTEM to demystify careers in science. Participation in ongoing efforts through the McAuliffe Center for Integrated Science Learning at Framingham State University will help educate middle and high school teachers and students on climate change. This project will support an existing female Ph.D. student at Boston College and an M.S. student at the University of Vermont. Summer undergraduate research assistants will be recruited through the Integrated Science for Society NSF REU at Boston College, which seeks to attract underrepresented minority and first-generation college students from schools with limited research opportunities.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.