Insights into Miocene to Quaternary Antarctic ice sheet variability from Scientific Drilling

Abstract:

A series of Antarctic drilling expeditions over the past 15 years have fundamentally altered the way that past variability of Antarctica’s ice sheets are considered within the Earth system. The ANDRILL project documented the first clear sedimentary evidence of West Antarctic ice sheet variability during the Pliocene, when the world was 2-3 degrees Celsius warmer and atmospheric levels of carbon dioxide were ~400 ppm. During these periods of past West Antarctic Ice Sheet collapse, summer sea ice in the Ross Sea was greatly reduced, and temperature proxies suggest waters were 3-4 degrees C warmer than present. The Integrated Ocean Drilling Program Expedition 318 in 2010, obtained records of climate and oceanographic changes from offshore of the Wilkes Subglacial Basin region of the East Antarctic Ice Sheet. This expedition provided new records of highly dynamic ice sheets in the Pliocene and Quaternary that demonstrated that marine-based sectors of East Antarctic Ice Sheet were also highly sensitive to climates similar to those projected in the near future. In 2018, International Ocean Discovery Program Expedition 374 was the latest phase of drilling in the Ross Sea and obtained cores that document in unprecedented detail the glacial and open marine conditions during the Middle Miocene Climate Optimum; as well as highly expanded offshore records of Plio-Pleistocene glacially-influenced oceanography. These records will provide novel insights into temperature changes immediately offshore of the marine-based West Antarctic Ice Sheet, in a critically sensitive region where changes in ocean heat flux are modelled to trigger past collapse events of ice sheets from the continental shelf edge. These new records will help ground-truth interpretations of large amplitude (~20-50m) eustatic sea level variations hypothesized from far-field and deep sea isotopic sea level records over the Miocene and Pliocene. While much knowledge has been gained via Antarctic scientific drilling over the past 15 years, many questions remain and future drilling plans and priorities in the Ross Sea and other sectors of Antarctica will also be discussed.