Massive Deglaciation in the South Shetland Islands (Antarctica) During Termination-1

Authors: Marc Oliva*, Universitat De Barcelona, Jesús Ruiz-Fernández, University of Oviedo, Spain, David Palacios, Complutense University of Madrid, José María Fernández-Fernández, Complutense University of Madrid, Irene Schimmelpfennig, Centre for Research and Teaching in Environmental Geoscience, Benjamín González-Díaz, University of Oviedo, ASTER Team, Centre for Research and Teaching in Environmental Geoscience
Topics: Polar Regions, Cryosphere, Geomorphology
Keywords: Antarctica, Byers Peninsula, deglaciation, surface exposure dating, nunataks.
Session Type: Paper
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Our knowledge of the calendar of deglaciation of the ice-free areas in the South Shetland Islands (SSI) is still limited. To this purpose, we have applied surface exposure dating methods using the in situ cosmogenic nuclide 36Cl to deglaciated polished surfaces on basaltic rocks. A total of 26 samples were collected in January’17 from three old volcanic plugs (Chester, Cerro Negro and Clark) that constituted nunataks during the last deglaciation. These hills are distributed across the central plateau of Byers Peninsula, the largest ice-free area in the SSI. Glacial thinning already started during the LGM, with the tops of nunataks becoming ice-free at 26-22.5 ka. A massive deglaciation occurred during Termination-1 between 17.4 and 14.3 ka followed by a relative stability of the ice cap until 11.4 ka. Subsequently, another phase of glacier retreat occurred until 7.5 ka and exposed the land surface in the central plateau where several lakes formed. This is also in agreement with lake records that also showed evidence that the Chester and Cerro Negro hills were no longer isolated nunataks by that time. Despite small Neoglacial advances, there was a gradual long-term glacial retreat eastwards between 6 and 2 ka followed by a relative glacier stability during the Late Holocene. These new results confirm that the first deglaciated environments in the northern Antarctic Peninsula appeared much earlier than known to date, which has major implications to understand ice-free terrestrial ecosystems, including geomorphic dynamics, permafrost distribution, vegetation colonization or soil processes.

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