The physiography of modern Antarctic subglacial lakes

The size and distribution of Antarctic subglacial lakes have been investigated using airborne radio-echo sounding (RES) and satellite radar altimetry. Over 70 lakes have been identified beneath the ice sheet from distinctive, mirror-like reflectors observed on RES records. Almost 60% of lakes are found within 200 km of an ice divide and only about 15% are located >500 km distant. The total volume of water stored in lakes beneath the Antarctic Ice Sheet is between 4000 and 12,000 km3. The bedrock topography of the ice-sheet interior is characterized by large subglacial basins separated by mountain ranges. More than 60% of lake records have marginal bed gradients of <0.1, implying that many Antarctic subglacial lakes are found in areas of relatively low bed relief, in and on the margins of subglacial basins. First, there are those lakes located where subglacial topography is relatively subdued, often towards the centre of subglacial basins. Secondly, some lakes occur in significant topographic depressions, closer to subglacial basin margins. Lakes are also found perched on the sides of subglacial mountains. Sixteen lakes are located close to the transition from slow to enhanced ice-sheet flow. Warm-based fast-flowing ice streams provide a possible route by which subglacial lakes may establish a hydrological connection with the ice-sheet margin. At a continental scale, the locations of Antarctic subglacial lakes match the modeled distribution of pressure melting at the ice-sheet bed.