NSFGEO-NERC Pliocene Sea Level Amplitudes (PLIOAMP)

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This project is jointly funded by the National Science Foundation’s Directorate of Geosciences (NSF/GEO) and the Natural Environment Research Council (NERC) of the United Kingdom (UK) via the NSF/GEO-NERC Lead Agency Agreement. This Agreement allows a single joint US/UK proposal to be submitted and peer-reviewed by the Agency whose investigator has the largest proportion of the budget. Upon successful joint determination of an award, each Agency funds the proportion of the budget and the investigators associated with its own component of the work. Projections of future sea-level rise from the Antarctic Ice Sheet vary widely and remain deeply uncertain. Of particular concern is the potential for marine-based sectors of the ice sheet to collapse and cause fast sea-level rise. The highest future sea-level projections come from a study that calibrated an ice-sheet model using sea-level data from the Pliocene epoch (5.3 to 2.6 Million years ago), based mainly on the elevation of ancient shorelines. However, recent work indicates that those former shorelines are too uncertain to be used as a model constraint. Independent and better-constrained estimates of Pliocene sea level are needed to determine ice-sheet sensitivity to climatic conditions warmer than today and to validate models used in future projections. This project aims to achieve that through reconstructing the amplitude of polar ice-volume change from proxy data recorded in marine sediments and then using these to validate and assess ice-sheet modeling approaches that simulate ice-volume change. The aims of the project are to 1) improve Pliocene sea-level estimates, 2) use the data to test and calibrate predictive ice-sheet models, and 3) to reduce uncertainty in future sea-level projections. The proposed workplan will determine if there was major retreat of the marine sectors of the Antarctic Ice Sheet during Pliocene warm intervals, and if processes capable of causing rapid sea-level rise such as marine-ice cliff failure are indeed required to explain past episodes of elevated sea level. The work plan will 1) reconstruct the amplitude of ice-volume change for multiple glacial-interglacial cycles during the mid-Pliocene using marine geochemical proxies, 2) simulate ice-volume change across these same cycles for both Antarctic and Northern Hemisphere ice sheets, 3) compare Antarctic ice sheet change in two models using parameterized and resolved grounding-line schemes, and 4) determine if marine ice-cliff failure is required to simulate the Pliocene dynamics. The new sea-level estimates will constrain Antarctic simulations under future climate change, producing projections of future sea level rise on century and longer timescales.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.