Abstract
Abstract. Basal hydrological systems play an important role in controlling the dynamic behaviour of ice streams. Data showing their morphology and relationship to geological substrates beneath modern ice streams are, however, sparse and difficult to collect. We present new multibeam bathymetry data that make the Anvers-Hugo Trough west of the Antarctic Peninsula the most completely surveyed palaeo-ice stream pathway in Antarctica. The data reveal a diverse range of landforms, including streamlined features where there was fast flow in the palaeo-ice stream, channels eroded by flow of subglacial water, and compelling evidence of palaeo-ice stream shear margin locations. We interpret landforms as indicating that subglacial water availability played an important role in facilitating ice stream flow and controlling shear margin positions. Water was likely supplied to the ice stream bed episodically as a result of outbursts from a subglacial lake located in the Palmer Deep basin on the inner continental shelf. These interpretations have implications for controls on the onset of fast ice flow, the dynamic behaviour of palaeo-ice streams on the Antarctic continental shelf, and potentially also for behaviour of modern ice streams.
Highlights
There is growing evidence that basal hydrology is a critical factor controlling the dynamic behaviour of ice streams (Bell, 2008; Christianson et al, 2014; Christoffersen et al, 2014), which account for most of the mass loss from large ice sheets
Integration of the new multibeam bathymetry data with preexisting data provides nearly continuous coverage of the Anvers-Hugo Trough (AHT) from Palmer Deep (PD) to beyond the continental shelf edge, with the new data spanning the full width of the trough on the middle shelf (Fig. 1)
mega-scale glacial lineations (MSGLs) in the midshelf part of the AHT have elongation ratios between 12 and 17 : 1, whereas some on the outer shelf have elongation ratios up to 80 : 1. The data confirm the occurrence of several grounding zone wedges (Fig. 1), some of which had been identified previously, indicating positions where the grounding zone paused during retreat from its Last Glacial Maximum (LGM) position (Larter and Vanneste, 1995; Vanneste and Larter, 1995; Batchelor and Dowdeswell, 2015)
Summary
There is growing evidence that basal hydrology is a critical factor controlling the dynamic behaviour of ice streams (Bell, 2008; Christianson et al, 2014; Christoffersen et al, 2014), which account for most of the mass loss from large ice sheets. Obtaining high resolution topographic data from modern ice stream beds that can reveal features associated with subglacial water flow is, logistically difficult and time consuming Modern ship-mounted sonar systems can be used to obtain such data efficiently over extensive areas of former ice stream beds on continental shelves that ice has retreated from since the Last Glacial Maximum (LGM; 23–19 ka cal BP). It is recognized that elongated drumlins and mega-scale glacial lineations (MSGLs) are signatures of past streaming ice flow on wet-based, mainly sedimentary beds, and that elonga-
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