CAREER: A Model-Based Rosetta Stone to Decipher the Stratigraphic Expression of Glacial Isostasy

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Rising sea levels will be among the most severe impacts of a warming climate on society. To assess the sensitivity of polar ice caps and sea-level change to increase in temperatures, this CAREER award examines how sediments accumulating on the shallow seafloor archive sea-level change. As ice sheets melt, the earth’s surface bends predictably in response to the shrinking weight of the ice sheets and ocean waters flooding continent edges. This bending causes local sea-level change to differ from the rise predicted if melt water evenly filled the world’s oceans, like a bathtub. The sea-level rise in response to a melting ice sheet will differ across the globe, with some sediment archives retaining a more accurate measure of sea-level change than others. This research will use computer models to make global maps of differences in sea-level change for two past geological epochs with temperatures higher than 21st century projections. Such maps will clarify the circumstances for which geologists can leverage the apparently different magnitudes of sea-level change from sediment archives around the globe to provide more accurate reconstructions of past ice sheet melt location and scale. This project advances climate understanding by creating a ‘Rosetta Stone’ to decode the magnitude of ancient sea-level change retained in coastal geology of past warm periods so as to refine future sea level projections. The integrated education plan will generate novel curriculum on the science and ethics of sea-level change to inspire university students to participate in a growing workforce addressing sea level projection and mitigation. The education plan will engage non-STEM undergraduates to create and disseminate artistic outreach products explaining geographic differences in sea-level change to the public.Collaboration between solid earth geophysicists and Quaternary stratigraphers has revealed that glacial isostatic adjustment (GIA) concurrently creates and destroys accommodation, such that the stratigraphic record of glacial–interglacial cycles should appear different from place to place; in turn spatial differences in contemporaneous local sea level deduced from the stratigraphic archive should provide insight into the magnitude and melt source of a deglaciation. This proposal undertakes numerical GIA simulations to ‘fingerprint’ spatial deviations from glacioeustasy for literature-proposed magnitudes and melt sources for the mid-Pliocene warm period and the Oligocene inception of the Antarctic ice sheet. These spatially variable sea-level records will then serve as inputs into a software that models how sedimentation and subsidence modulate how GIA manifests in stratigraphy. The results will serve to decode spatial patterns in sea level retained in ice-age stratigraphy applicable across the geological timescale.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.