Characterizing Subglacial Hydrology Within the Amery Ice Shelf Catchment Using Numerical Modeling and Satellite Altimetry

Meltwater forms at the base of the Antarctic Ice Sheet due to geothermal heat flux (GHF) and basal frictional dissipation. Despite the relatively small volume, this water has a profound effect on ice-sheet dynamics. However, subglacial melting and hydrology in Antarctica remain highly uncertain, limiting our ability to assess their impact on ice-sheet dynamics. Here we examine subglacial hydrology within the Amery Ice Shelf catchment, East Antarctica, using the subglacial hydrology model GlaDS. We calculate subglacial melt rates using a higher-order ice-flow model and two GHF estimates. We find a catchment-wide melt rate of 7.03 Gt year-1 (standard deviation = 1.94 Gt year-1), which is >= 50% greater than previous estimates. The contribution from basal dissipation is approximately 40% of that from GHF. However, beneath fast-flowing ice streams, basal dissipation is an order of magnitude larger than GHF, leading to a significant increase in channelized subglacial flux upstream of the grounding line. We validate GlaDS using high-resolution interferometric-swath radar altimetry, with which we detect active subglacial lakes and fine-scale ice-shelf basal melting. We find a network of subglacial channels that connects areas of deep subglacial water coincident with active subglacial lakes, and channelized discharge at the grounding line coinciding with enhanced ice-shelf basal melting. The concentrated discharge of meltwater provides 36% of the freshwater released into the ice-shelf cavity, in addition to ice-shelf basal melting. This suggests that ice-shelf basal melting is strongly influenced by subglacial hydrology and could be affected by future changes in subglacial discharge, such as lake drainage or channel rerouting. Melting beneath the Antarctic Ice Sheet is relatively low, but the pattern of melting and meltwater drainage is important for controlling the flow of the overlying ice. Melting occurs due to geothermal heating from the underlying bedrock and heat generated from friction as the ice slides over the bedrock. Despite its importance, we know very little about melting beneath the Antarctic Ice Sheet. Here we use a numerical model to calculate meltwater drainage pathways beneath part of the ice sheet that flows into the Amery Ice Shelf, East Antarctica. We find that total melting is 7 gigatonnes per year. This is 50% more than previous studies because our model can resolve high melting beneath areas where the ice sheet is flowing fast. Using satellite observations of ice-sheet surface elevation change, we detect the filling and draining of lakes at the base of the ice sheet and ocean melting beneath the floating ice shelf. We use these observations to validate the modeled meltwater drainage pathways at the base of the ice sheet. These findings suggest that meltwater drainage from the base of the ice sheet may play an important role in controlling ocean melting of the floating ice shelf. We use the spatial distribution of ice-shelf basal melting and location of active subglacial lakes to validate a subglacial hydrology model Subglacial channels link subglacial lakes and focus meltwater discharge at the grounding line, triggering enhanced ice-shelf melting Modelled total subglacial melt is 7 Gt yr-1 and contributes 36% of the freshwater released in the ice-shelf cavity