The supply of subglacial meltwater to the grounding line of the Siple Coast, West Antarctica

Abstract

AbstractRecent satellite studies have shown that active subglacial lakes exist under the Antarctic ice streams and persist almost to their grounding lines. When the lowest-lying lakes flood, the water crosses the grounding line and enters the sub-ice-shelf cavity. Modeling results suggest that this additional freshwater influx may significantly enhance melting at the ice-shelf base. We examine the spatial and temporal variability in subglacial water supply to the grounding lines of the Siple Coast ice streams, by combining estimates for lake volume change derived from Ice, Cloud and land Elevation Satellite (ICESat) data with a model for subglacial water transport. Our results suggest that subglacial outflow tends to concentrate towards six embayments in the Siple Coast grounding line. Although mean grounding line outflow is ~60m3 s–1 for the entire Siple Coast, maximum local grounding line outflow may temporarily exceed 300 m3 s–1 during the synchronized flooding of multiple lakes in a hydrologic basin. Variability in subglacial outflow due to subglacial lake drainage may account for a substantial portion of the observed variability in freshwater flux out of the Ross Ice Shelf cavity. The temporal variability in grounding line outflow results in a net reduction in long-term average melt rate, but temporary peak melting rates may exceed the long-term average by a factor of three.