Abstract
Abstract. Studying the history of ice-sheet behaviour in the Ross Sea, Antarctica's largest drainage basin can improve our understanding of patterns and controls on marine-based ice-sheet dynamics and provide constraints for numerical ice-sheet models. Newly collected high-resolution multibeam bathymetry data, combined with two decades of legacy multibeam and seismic data, are used to map glacial landforms and reconstruct palaeo ice-sheet drainage. During the Last Glacial Maximum, grounded ice reached the continental shelf edge in the eastern but not western Ross Sea. Recessional geomorphic features in the western Ross Sea indicate virtually continuous back-stepping of the ice-sheet grounding line. In the eastern Ross Sea, well-preserved linear features and a lack of small-scale recessional landforms signify rapid lift-off of grounded ice from the bed. Physiography exerted a first-order control on regional ice behaviour, while sea floor geology played an important subsidiary role. Previously published deglacial scenarios for Ross Sea are based on low-spatial-resolution marine data or terrestrial observations; however, this study uses high-resolution basin-wide geomorphology to constrain grounding-line retreat on the continental shelf. Our analysis of retreat patterns suggests that (1) retreat from the western Ross Sea was complex due to strong physiographic controls on ice-sheet drainage; (2) retreat was asynchronous across the Ross Sea and between troughs; (3) the eastern Ross Sea largely deglaciated prior to the western Ross Sea following the formation of a large grounding-line embayment over Whales Deep; and (4) our glacial geomorphic reconstruction converges with recent numerical models that call for significant and complex East Antarctic ice sheet and West Antarctic ice sheet contributions to the ice flow in the Ross Sea.
Highlights
The Ross Embayment drains ∼ 25 % of the Antarctic ice sheet into the Ross Sea and is the largest ice drainage basin in Antarctica, fed by multiple ice streams sourced from the East Antarctic (EAIS) and West Antarctic (WAIS) ice sheets (Fig. 1)
Multibeam bathymetry provides a direct record of bed conditions beneath the former ice sheet, revealing landforms associated with past ice flow
A few small grounding zone wedges (GZWs) occur along the flanks of the trough; otherwise the mega-scale glacial lineations (MSGLs) are not overprinted by recessional features
Summary
The Ross Embayment drains ∼ 25 % of the Antarctic ice sheet into the Ross Sea and is the largest ice drainage basin in Antarctica, fed by multiple ice streams sourced from the East Antarctic (EAIS) and West Antarctic (WAIS) ice sheets (Fig. 1). The nature of ice-sheet palaeodrainage and retreat in the Ross Sea has significant implications for understanding the dynamics of the WAIS and EAIS, and their respective sensitivities to factors that govern ice behaviour. Multibeam bathymetry provides a direct record of bed conditions beneath the former ice sheet, revealing landforms associated with past ice flow These landforms document the flow behaviour of formerly grounded ice. Here we compile legacy multibeam bathymetry data from 41 cruises over the last 20 years (Supplement Table 1), combined with recently acquired high-resolution multibeam data, to characterise glacial geomorphic features across the Ross Sea. This
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