PP014-03
What can advances in Antarctic deglacial sediment 14C dating tell us about grounding line evolution?

Tuesday, 8 December 2020: 17:38
Virtual
Brad E Rosenheim1, Ryan Venturelli2, Cristina Subt3, Imogen Mireille Browne4, Theresa M King5, Timothy Campbell6, Philip J Bart7, John E Dore8, David M Harwood9, Jonathan Kingslake10, Jae-Il Lee11, Amy Leventer12, Alexander B Michaud13, Molly Patterson14, Amelia Shevenell15, Matthew Siegfried16, Mark L Skidmore6, Kyu-Cheul Yoo11, Ho Il Yoon17 and SALSA Science Team, (1)University of South Florida St. Petersburg, St Petersburg, FL, United States, (2)University of South Florida, St Petersburg, United States, (3)El Paso Community College, Geological Sciences, El Paso, TX, United States, (4)University of University of South Florida,, St. Petersburg, FL, United States, (5)University of South Florida, College of Marine Science, Tampa, FL, United States, (6)Montana State University, Earth Sciences, Bozeman, MT, United States, (7)Louisiana State Univ, Baton Rouge, LA, United States, (8)Montana State University, Department of Land Resources and Environmental Sciences, Bozeman, MT, United States, (9)University of Nebraska Lincoln, Lincoln, NE, United States, (10)Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY, United States, (11)Korea Polar Research Institute, Incheon, South Korea, (12)Colgate University, Geology, Hamilton, NY, United States, (13)Bigelow Lab for Ocean Sciences, East Boothbay, ME, United States, (14)Binghampton University, Binghamton, NY, United States, (15)University of South Florida, Tampa, FL, United States, (16)Colorado School of Mines, Geophysics, Golden, CO, United States, (17)KOPRI, Incheon, South Korea
Recorded Presentation
Abstract:
Advances in dating Antarctic margin sediments are improving understanding of the overall retreat of grounding lines and ice shelves/calving fronts since the last glacial maximum (~25,000 years ago). Radiocarbon (14C) dating of glaciomarine sediments from other periods before and after the deglaciation demonstrates that dynamic ice behavior was not limited, however, to the deglaciation. The timing and patterns of deglaciation vary around Antarctica, and not always linearly with global and regional climate and sea level records. For instance, Ross Sea 14C records suggest icesheet margin fluctuations in the form of ice-proximal glaciomarine sediment overlying open ocean sediment that dates to ~24,000 years ago (AIM 2) in the western Ross Sea (Drygalski Ice Tongue). Farther east in the Ross Sea, marine carbon input beneath the Whillans and Mercer Ice Streams (Whillans Grounding Zone and Mercer Subglacial Lake, respectively) is evident during the mid-Holocene. Both the AIM2 excursion and the mid-Holocene have been shown to be relatively warmer periods, albeit during different glacial regimes, yet they result in different ice-climate responses. Additionally, 14C records from the Whales Deep cross-shelf trough in the eastern Ross Sea suggest several hundreds of years between ice shelf collapse and grounding line retreat. The implication is that past interactions between ice shelves and ice sheets differ from our current understanding of ice dynamics based on contemporary observations. Here, we outline new 14C dating results that have led to our observations from around the Ross Sea and discuss the implications for our understanding of ice dynamics. Establishing ways to use such observations to verify ice dynamics models should be a primary focus to improve our knowledge of internal ice dynamics versus responses to external forcings such as climate and sea level change. Ultimately, we may be able to better forecast the key instabilities of future changes in Antarctica that would affect current human civilization through sea level rise.
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