Relative temporal stability of the Antarctic ice sheets during the late Neogene based on the minimum frequency of outer shelf grounding events

Abstract

The stability of the Antarctic cryosphere involves two fundamental aspects: the magnitude of ice volume changes, and the frequency of ice volume changes. In this article, we synthesize results from three regional seismic stratigraphic studies of the continental shelf to evaluate the relative frequency of extreme advances of the ice sheets during the late Neogene for different sectors of the Antarctic ice sheet. Detailed analyses of glacial unconformities on the eastern and western Ross Sea outer continental shelf indicate that there were at least eight episodes during the late Neogene when the East Antarctic ice sheet (EAIS) and the West Antarctic ice sheet (WAIS) were significantly larger. The seismic results from the shelf do not support the conventional view that the land-based EAIS was relatively stable and that the marine-based WAIS was relatively dynamic. Glacial unconformities on the Pacific continental shelf of the Antarctic Peninsula indicate that there were at least 30 outer shelf ice sheet expansions during the late Neogene. This suggests that the small land-based Antarctic Peninsula Ice Cap (APIC) may have been the most dynamic component of the Antarctic cryosphere. Conversely, the greater number of grounding events on the Antarctic Peninsula shelf may be a result of the margin’s younger thermal age and hence greater potential to preserve units and unconformities during the late Neogene. We acknowledge that the available chronostratigraphic control from the Antarctic margin is poor, and that more chronological data are needed to confirm our late Neogene age assignments.