Bounding global ice volumes over the last glacial cycle using reconstructions of Bering Strait flooding

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The stability of Earth’s ice sheets in the past informs our understanding of their resilience in the face of a warming climate. Knowing the magnitude and timing of global ice sheet changes is important for understanding how past ice sheet change related to climate change. However, we know little about how dynamic ice sheets were prior to 26,000 years ago, when ice sheets were at their largest. This project will use new geochemical tools to tell when the Bering Strait was flooded or exposed during the last glacial cycle (the past 120,000 years). In combination with computer model simulations, this information will be used to bound previously unknown global ice volume histories over this time. Further, this project will support a PhD student, who will learn about how science can produce social inequities through the UC Santa Cruz Science & Justice Research Center. PI Pico will develop innovative teaching tools for making legible the roots of geoscience culture in scientific racism and imperialism. These tools will be included in courses taught at UC Santa Cruz and Princeton. Finally, all personnel will participate in the outreach to the Alaska Native Science & Engineering Program.The history of global ice sheet growth leading into the Last Glacial Maximum is poorly constrained, as advancing ice sheets and subsequent sea-level rise during deglaciation destroyed evidence of past ice margins and coastlines. To address this uncertainty, this project will develop a continuous, non-traditional sea-level reconstruction over the last glacial cycle (120,000 years) by constraining the flooding history of the Bering Strait. Measuring nitrogen isotope ratios of organic matter protected within the shell walls of Arctic planktic foraminifera will elucidate the past connectivity of the North Pacific and Arctic Oceans, thus constraining the local sea-level history at the Bering Strait. State-of-the-art glacial isostatic adjustment sea-level simulations will be performed using the range of uncertainty on global ice volumes to model local sea level at the Bering Strait. Finally, this continuous Bering Strait flooding reconstruction will be used to test the plausibility of different global ice volume histories, and thus bound global mean sea-level highstands and lowstands before the Last Glacial Maximum.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.