Rapid deglacial retreat of a regional scale ice stream and late Holocene readvance in Vincennes Bay, east Antarctica

Abstract

Vincennes Bay provides a unique opportunity to understand the role of bed topography on modulating deglaciation in East Antarctica. Here, one of the deepest troughs on the margin (Vanderford Trough), lies adjacent to a terrestrially grounded, independent ice dome (Law Dome). Thus, we contrast the deglacial history of these systems and provide insights into future ice loss in parts of the continent underlain by large subglacial basins. We use multibeam bathymetry to map the ice retreat of these systems and cosmogenic nuclide dating onshore, to constrain timing. Bedforms suggest at least two phases of retreat across the continental shelf, separated by a large mid-shelf ridge. Seaward of the ridge, bedforms evidence ice sheet expansion to the continental shelf break. Landward of the ridge distinct bedforms, combined with synchronous exposure of the Windmill Islands and Snyder Rocks ∼10 ka, are consistent with a Marine Ice Sheet Instability style retreat into the overdeepened troughs. This timing evidences a distinct difference in deglacial histories in East Antarctica, with regions east of 60°E stabilising several thousand years earlier than to the west. We explore drivers of this divergence, including the potential for continental shelf geometry to limit warm water incursion to overdeepened grounding lines. Lastly, a gap in exposure age distribution and the reworking of marine material into modern day shear moraines suggest the western margin of Law Dome was retreated further than present ∼5.7 to 2.3 ka, with re-advance potentially driven by a strengthening of easterly winds after ∼4 ka.