Hydrological networks beneath Antarctica: New signals from altimetry
Andrew Shepherd(1) and Duncan Wingham(2)
Scott Polar Research Institute,
Cambridge CB2 1ER,
(2) University College London, Gower Street, London WC1E 6BT, United Kingdom
While much of the base of the East Antarctic ice sheet is melting, as is evident from 145 subglacial lakes, little else is known about the basal hydrology of this huge ice mass. Such knowledge is critical to understanding the flow of ice, the rate at which water stored beneath an ice mass may be transferred to its margin, the development of glacial landforms and the habitats of subglacial lakes. In addition, little attention has been given to the possibility that the very existence of subglacial lakes may determine the mode of basal drainage through intense outburst flooding. Here we record an outburst flood from a subglacial lake within the Adventure Subglacial Trench in central East Antarctica, the most stable part of the ice sheet. We show that, in 16 months, some 1.8 cubic kilometres of flood water was transferred 290 km to at least two other subglacial lakes. While the presence of the ice roof may moderate flooding, the intrinsic instability of pressurising subglacial lakes makes such events, occurring at intervals of 10 to 1000 years, a normal mode of subglacial drainage. If large lakes, such as Lake Vostok or Lake Concordia, are presently pressurising, substantial floods may be foreseen, and these may reach the coast. Our observations are also in contrast to expectations that subglacial lakes are characterised by long residence times and slow circulations; indeed entire subglacial drainage basins may be flushed at regular intervals. The rapid transfer of water from one lake to another will result in the large-scale relocation of solute and microbes between lakes, and the contamination of significant portions of drainage systems from future in situ exploration is a distinct risk.