Catchment Boundary Delineation of Greenlandic and Antarctic Ice Sheets

Geothermal and mechanical dissipation of heat due to basal sliding and deformation give rise to melting at the base of the ice sheets. This large volume of water follows paths of maximum pressure gradients and discharges to the ocean. Here, we delineate the direction of flow of subglacial melt water by partitioning maps of the hydrologic head of Antarctica and Greenland into major drainage basins based on maximum gradients. Balance velocity, elevation, ice thickness and basal topography data gridded at a 5-Km resolution was utilized to define each major catchment boundary. Each of these drainage basins was compiled into a single grid for each ice sheet. The subglacial water catchment boundaries closely resemble that of the overlying ice sheet's glacier catchment boundaries, as is expected since since subglacial water pressure depends about ten times more strongly on surface slope than basal slope. An estimation of the total volume of basal melt water produced per annum at the terminus of the major outlet glaciers was additionally calculated using the catchment boundary maps. This has important implications for the dynamics of buoyant fresh melt water plumes in sub ice shelf cavities and tidewater glacier fronts.