C024-11
Applications of in situ 14C to ice thickness changes in western Dronning Maud Land, East Antarctica

Wednesday, 9 December 2020: 06:01
Virtual
Sarah Sams1, Nathaniel A Lifton1, Jane Lund Andersen2, Jennifer Newall3, Robin Blomdin3,4, Derek Fabel5, Ola Fredin6, Neil F Glasser7, Jon Harbor8, Alexandria Koester1, Arjen P Stroeven3, Marc Caffee9, Brent M Goehring10 and Keir Alexander Nichols10, (1)Purdue University, Department of Earth, Atmospheric, and Planetary Sciences, West Lafayette, IN, United States, (2)Aarhus University, Department of Geoscience, Aarhus, Denmark, (3)Stockholm University, Department of Physical Geography, Stockholm, Sweden, (4)Geological Survey of Sweden, Department of Physical Planning, Uppsala, Sweden, (5)Scottish Universities Environmental Research Center, East Kilbride, United Kingdom, (6)Norwegian University of Science and Technology, Department of Geography, Trondheim, Norway, (7)Aberystwyth University, Department of Geography and Earth Sciences, Aberystwyth, United Kingdom, (8)Purdue University Global, West Lafayette, IN, United States, (9)Purdue University, Purdue Rare Isotope Measurement Laboratory, West Lafayette, IN, United States, (10)Tulane University of Louisiana, Department of Earth and Environmental Sciences, New Orleans, LA, United States
Abstract:
Reconstructing ice-sheet elevations of the East Antarctic Ice Sheet (EAIS) is vital to understanding its response to past climate changes. Numerical ice-sheet models are used to make these reconstructions, drawing on theory and empirical evidence, such as data from geomorphic features indicating its former extent and thickness and from ice cores. However, in western Dronning Maud Land (DML), field-based evidence has been lacking previously (Newall et al., 2020; Journal of Maps, 16: 468-478). To fill this data gap, we employed cosmogenic nuclide exposure dating of bedrock and erratic samples from nunataks – areas of exposed bedrock that protrude through the contemporary ice surface. Cosmogenic nuclide inventories of these samples record evidence of ice-sheet thickness changes. Long-term ice thickness histories can be constrained using long-lived cosmogenic nuclides, such as 10Be (t1/2 1.4 My), 21Ne (stable), 26Al (t1/2 705 ky), and 36Cl (t1/2 301 ky). However, these often preserve complex histories of burial and exposure that can mask ice-cover histories since the Last Glacial Maximum (LGM). In situ cosmogenic 14C (in situ 14C), by virtue of its short half-life (t1/2 5.7 ky), is sensitive to complex exposure/burial scenarios in this time frame, and is thus the best tool for understanding exposure histories since the LGM.

MAGIC-DML is an ongoing Swedish-US-Norwegian-German-UK collaboration focused on understanding past ice-sheet changes in western DML. During the 2016/17 and 2017/18 austral summers, we collected samples from erratic boulders and glacially-molded bedrock for cosmogenic nuclide exposure dating. Samples were collected in the Heimefrontfjella, Vestfjella, Ahlmannryggen, Borgmassivet, and Sverdrupfjella nunatak ranges. The MAGIC-DML research group has so far analyzed quartz-bearing samples for 10Be, 21Ne, and 26Al, and mafic lithologies for 36Cl, which provide insights into the long-term ice histories of the region. In conjunction with the previous nuclides, 22 samples have recently been analyzed for in situ 14C to constrain post-LGM exposure histories of the western DML sector of the EAIS. In situ 14C data and interpretations presented here are the first of their kind from western DML.
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