The West Antarctic Ice Sheet contains 3.8 million cubic kilometres of ice. If it ever disintegrated, releasing this volume into the ocean, the rise in sea level could be as much as six metres. But will global warming ever make this happen? In the 2 July 1998 issue of Nature, two reports describe how the size and location of fast-flowing ice streams, which drain ice into the sea, are affected by the underlying geology. This should eventually help scientists to predict how the ice sheet will respond to changes in climate.
Sea level is rising by about 20 centimetres per century at the moment. This modest rise contrasts with the dramatic changes that occurred at the end of the last Ice Age, when ice-sheet melting caused sea level to rise at rates of up to several metres per century. Average global temperatures may then have been only 2 °C higher than now, raising concerns about the effects of global warming. Ideally we need to know whether the present-day ice sheets could melt or collapse that quickly, and to be able to predict when, and how rapidly.
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