Collaborative Research: How much and why did Ice Sheets melt during the Last Interglacial (HISEAS)

To better understand how ice sheets will respond to future warming, scientists have been studying time periods in Earth’s past when temperatures were naturally warmer than they are today. This project focuses on the Last Interglacial, a time period approx. 130,000 to 115,000 years ago, which marks the most recent time in Earth’s history when the Greenland and Antarctic ice sheets were significantly smaller than they are today. The project aims to better understand when and how much these two major ice sheets melted, as well as what climate conditions and ice dynamical processes drove their mass loss. Understanding the factors that drove ice sheet melt in the past will help improve predictions of future ice sheet change. Project goals will be reached through a combination of fieldwork to obtain new estimates of past sea level, laboratory analyses to reconstruct past climate conditions, and modeling to simulate data-informed sea level, ice sheet, and climate histories. Project results will contribute to international efforts that inform policymakers of climate change through the Intergovernmental Panel on Climate Change (IPCC). Fieldwork at multiple locations will connect the project team with local researchers and communities to understand their needs and regional impacts of sea level change. The HISEAS project will use the Earth system model CLIMBER-X coupled with the ice sheet model PISM and sea level model VILMA to simulate ice sheet and sea-level evolution from the penultimate glacial maximum to the end of the Last Interglacial (140 – 115 thousand years ago). The model will be calibrated with a range of existing and new paleoclimatological data. Data products will include (1) a new comprehensive database of terrestrial and sea-surface temperature, iceberg discharge, sea-ice extent, deep ocean circulation, and vegetation data; (2) new paleoclimate records relevant to understanding climate-ice-sheet interactions (e.g., sea surface temperature, iceberg discharge, and sea-ice extent) using existing deep-sea sediment cores as well as fossil corals; and (3) new sea-level records from four locations paired with an existing database of Last Interglacial sea-level proxies. A sea-level fingerprint analysis will complement the Earth system modeling to provide a parallel estimate of ice sheet change during the Last Interglacial. The data-calibrated models will allow the researchers to evaluate the roles of external drivers (e.g., temperatures and precipitation), boundary conditions (e.g., bedrock elevation), and internal ice sheet processes in driving ice sheet change during the Last Interglacial period. 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.