COLLABORATIVE RESEARCH: Site Survey for Subglacial Bedrock Exposure Dating at the Margin of the Wilkes Basin in Northern Victoria Land

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The goal of this project is to establish, through direct geological evidence, whether complete deglaciation of East Antarctic marine basins took place during past warm-climate periods. Direct geological information about whether the Antarctic Ice Sheet responded catastrophically to past climate changes is important to evaluating the likelihood of significant ice-sheet response to future climate change. The team will assess the feasibility of achieving this goal using cosmogenic-nuclide measurements on bedrock that is currently buried under the ice sheet. They will conduct a reconnaissance and site survey to identify potential drill sites where subglacial bedrock-exposure dating could subsequently be used to test whether ice at those sites was absent when the Earth last experienced current levels of carbon dioxide—at approximately 3.0 to 3.3 million years ago.This project will seek out potential sites that can address whether total deglaciation of subglacial basins in coastal East Antarctica took place during past warm-climate periods like the middle Pliocene warm period at circa 3.0-3.3 Ma. Ice-sheet model simulations have identified marine ice-margin instability as a possible cause for higher eustatic sea level during this period. In general, it is difficult to obtain direct and unambiguous geological evidence that an ice sheet was smaller in the past because if such evidence exists it is most likely inaccessible beneath the present ice sheet. One means of overcoming this problem is to search for significant concentrations of cosmic-ray-produced radionuclides in bedrock surfaces beneath the present ice sheet. Such concentrations can only be produced if the surface is ice-free, so significant cosmogenic-nuclide concentrations would provide incontrovertible evidence that the ice sheet was smaller in the past, and, in addition, can provide information about when this occurred. Guided by ice-sheet model simulations of Pliocene deglaciation to identify areas where complete deglaciation of the Wilkes subglacial basin would cause substantial changes in the extent of bedrock exposure, the team will collect geophysical and geochemical data to identify and evaluate sites with potential for future bedrock recovery.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.