Postdoctoral Fellowship: OCE-PRF: Constraining the timing and magnitude of sea-level change in a warm world

The behavior of ice sheets during past warm periods can be used to help us better project how ice sheets and sea level will respond in the future under conditions of sustained warming. In turn, this knowledge can be leveraged to help build more resilient coastal communities and protect and defend our coastlines. Currently there is debate about the dynamics of the polar ice sheets during the most recent past warm period in the geological record, known as the Last Interglacial around 125,000 years ago. Some reconstructions for this time interval suggest a stable/slow rising sea level from ice sheets retreat, while others cite evidence consistent with more variable sea level from rapid ice sheet volume changes. While evidence for this problem remains controversial, a new methodology was recently applied, and firm evidence was found for a brief local fall in sea level at a single location. However, the timing and rate of sea level change are still poorly constrained, and the global extent of this feature remains unknown. This project seeks to build on this new approach and combine it with high-precision dating to refine our understanding of the rates and extent of Last Interglacial ice sheet retreat and sea level change. This project will provide professional development and mentoring opportunities for the fellow and develop a virtual field trip website using drone and other imagery to expand accessibility of sea level research.

Shallow marine carbonates such as coral reefs can be used to help reconstruct the magnitude of past sea level changes. This project will leverage existing samples collected from fossil coral reefs around the globe that grew during the Last Interglacial. The focus will be on Last Interglacial coral reef deposits in Western Australia and the Seychelles that contain three distinct generations of reef growth separated by disconformities or transitional sedimentary facies, to test the question of sea-level variability. The main goals of the project are (1) to assess whether there is evidence of subaerial exposure associated with the sedimentary surfaces bounding the reef units and (2) define the time represented between the deposition of reef units. New cutting-edge, super resolution autofluorescence (SRAF) microscopy that can reveal fine-scale carbonate petrography will be combined with U-series coral geochronology within detailed stratigraphic frameworks to determine the timing and magnitude of potential subaerial exposure events and to correlate observed relative sea-level change between sites. This project will produce important proxy data to calibrate and improve ice sheet models to determine which ice sheets were most susceptible to past warming and how future ice sheet retreat will affect U.S. and global coastlines.

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.

Award Number: 2512958
Principal Investigator: Kyle Fouke
Funds Obligated: $322,497
State: WI