Abstract
AbstractThree holes were drilled to the bed of Rutford Ice Stream, through ice up to 2154 m thick, to investigate the basal processes and conditions associated with fast ice flow and the glacial history of the West Antarctic Ice Sheet. A narrative of the drilling, measuring and sampling activities, as well as some preliminary results and initial interpretations of subglacial conditions, is given. These were the deepest subglacial access holes ever drilled using the hot-water drilling method. Samples of bed and englacial sediments were recovered, and a number of instruments were installed in the ice column and the bed. The ice–bed interface was found to be unfrozen, with an existing, well-developed subglacial hydrological system at high pressure, within ~1% of the ice overburden. The bed itself comprises soft, water-saturated sediments, consistent with previous geophysical interpretations. Englacial sediment quantity varies significantly between two locations ~2 km apart, and possibly over even shorter (~20 m) distances. Difficulties and unusual observations encountered while connecting to the subglacial hydrological system in one hole possibly resulted from the presence of a large clast embedded in the bottom of the ice.
Highlights
The biggest uncertainty in our ability to predict future sea level rise comes from the polar ice sheets
The load fluctuations on the drill tower observed while drilling the lower parts of all three holes, combined with the sedimentary material recovered from the drill stem in Holes 2 and 3, confirm the presence of significant amounts of englacial sediment in the basal ice in this region, consistent with geophysical interpretations (Smith, 1996)
Three holes were successfully drilled to the bed of Rutford Ice Stream during the BEAMISH Project, through ice up to 2154 m thick
Summary
The biggest uncertainty in our ability to predict future sea level rise comes from the polar ice sheets. This fact is important and pertinent because sea level rise from ice sheets is increasing faster than expected and because ice-sheet processes have the potential to trigger irreversible sea level rise that would continue for many centuries (Oppenheimer and others, 2019). Reducing this uncertainty is currently one of the biggest challenges in glaciology. Ice stream beds have been accessed in very few locations and observational data to support ice-sheet models remain extremely sparse
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