Collaborative Research: EAGER: Dating Glacier Retreat and Readvance near Mount Waesche, West Antarctica

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Obtaining glaciological and geologic data on the size of the West Antarctic Ice Sheet between the last two glacial periods (125,000 years ago), when global temperatures and sea level were higher than today, provides direct constraints on the ice sheet’s response to warmer climate. These data also provide validation points for ice-sheet models used to project future sea level. However, obtaining these data is difficult as the evidence for between glacial period ice extent lies below the present ice surface. A key location for determining this ice extent is Mount Waesche, a volcano that rises above the ice surface near the dome of the ice sheet. In preparation for drilling through the ice to obtain rock cores from lava flows that extend under the ice sheet, the team previously used ground-penetrating radar to map the sub-ice topography and internal glacial layering. These radar profiles revealed discontinuities within the ice that represent lower ice levels that may have occurred during the last between glacial periods. The ice-core work to be added through this award aims to enhance the team’s rock core drilling program at Mount Waesche by dating the discontinuities in the ice. Knowing the age of the discontinuities would provide independent evidence for past ice levels. Similar internal glacial discontinuities have been observed in radar profiles elsewhere in Antarctica; if the team is successful dating them at Mount Waesche, the technique could have wider application for constraining lower ice-sheet levels across Antarctica.To maximize scientific return from the rock-drilling portion of the project, the team will collect and analyze ice samples to constrain the ages of englacial unconformities. Specifically, the team will obtain vertical ice cores that include the englacial unconformities using the Eclipse Drill and surface horizontal cores that sample exposed englacial tephra stratigraphy extending back to 118,000 years before present using a horizontal ice trencher. The team will extrapolate the resulting surface chronology to subsurface depths using radar, providing lateral depth-age constraints of stratigraphy. Isotopic and tephra analysis will be used to provide age constraints on the ice cores. These data will be correlated with other, well-dated West Antarctic ice cores to obtain a local chronology and date the unconformities. The goal of this exploratory work is to provide data that complement the results from subglacial rock cores to better constrain surface-elevation change, including both retreat and readvance, since the last interglacial.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.