Wingham Duncan J, Siegert Martin J, Shepherd Andrew, Muir Alan S
Centre for Polar Observation and Modelling, Department of Space and Climate Physics, Pearson Building, University College London, Gower Street, London WC1E 6BT, UK.
Nature. 2006 Apr 20;440(7087):1033-6. doi: 10.1038/nature04660.
The existence of many subglacial lakes provides clear evidence for the widespread presence of water beneath the East Antarctic ice sheet, but the hydrology beneath this ice mass is poorly understood. Such knowledge is critical to understanding ice flow, basal water transfer to the ice margin, glacial landform development and subglacial lake habitats. Here we present ice-sheet surface elevation changes in central East Antarctica that we interpret to represent rapid discharge from a subglacial lake. Our observations indicate that during a period of 16 months, 1.8 km3 of water was transferred over 290 km to at least two other subglacial lakes. While viscous deformation of the ice roof above may moderate discharge, the intrinsic instability of such a system suggests that discharge events are a common mode of basal drainage. If large lakes, such as Lake Vostok or Lake Concordia, are pressurizing, it is possible that substantial discharges could reach the coast. Our observations conflict with expectations that subglacial lakes have long residence times and slow circulations, and we suggest that entire subglacial drainage basins may be flushed periodically. The rapid transfer of water between lakes would result in large-scale solute and microbe relocation, and drainage system contamination from in situ exploration is, therefore, a distinct risk.
众多冰下湖的存在为东南极冰盖下广泛存在水体提供了明确证据，但对该冰体下的水文情况却知之甚少。此类知识对于理解冰流、冰底水向冰缘的转移、冰川地貌发育以及冰下湖栖息地至关重要。在此，我们展示了东南极洲中部冰盖表面的高程变化，我们将其解释为一个冰下湖的快速排水。我们的观测表明，在16个月的时间里，1.8立方千米的水被输送了290千米，至少流入了另外两个冰下湖。虽然上方冰盖的粘性变形可能会减缓排水，但这样一个系统的内在不稳定性表明，排水事件是冰底排水的一种常见模式。如果像沃斯托克湖或康科迪亚湖这样的大湖处于高压状态，那么大量排水有可能抵达海岸。我们的观测结果与冰下湖停留时间长且循环缓慢的预期相矛盾，我们认为整个冰下排水盆地可能会定期被冲刷。湖泊之间水的快速转移将导致大规模的溶质和微生物迁移，因此，原位勘探造成排水系统污染是一个明显的风险。
