Climate change: Antarctica's glacier

ONE OF the biggest glaciers in the Antarctic is melting faster than it is forming, say scientists measuring its demise by satellite radar. Since 1992, the melting of the Pine Island Glacier, the largest on the West Antarctic Ice Sheet, has dumped an extra 31 cubic kilometres of ice from the frozen interior of the South Pole into the sea.

Satellite images show the glacier has thinned by 1.6 metres (5ft 2in) a year. If it melted completely it would raise sea levels by 6mm (0.2in) but if the whole ice sheet disappeared, sea levels would rise a catastrophic five metres (16ft).
British scientists, led by Andrew Shepherd of University College London, cannot fully explain the melting and have no direct evidence that it is due to global warming, predicted to thicken some Antarctic glaciers because of increased snowfall.
Scientists believe the phenomenon cannot be due to seasonal fluctuations caused, for example, by strong winds evaporating ice. "We should be concerned that a section of Antarctica is thinning like no other part of the continent," Dr Shepherd said. "If this is an accelerating phenomenon then the timescales of the glacier's retreat and the mass of water being discharged into the ocean could be significantly increased," he said.
The study of the Pine Island Glacier, published in the journal Science, is considered important because the glacier transports large volumes of ice from deep within the interior of the frozen ice sheet towards the sea. One worrying scenario is that if the melting observed by the two European Remote Sensing satellites gets worse, it could trigger a wider destabilisation of the ice sheet, leading to the prospect of ever-rising sea levels.
For the past 25 years there has been speculation about whether a retreat of a West Antarctic glacier could accelerate ice flow from its interior producing a rise in sea levels. We have shown for the first time that such a retreat is indeed occurring," Dr Shepherd said.
"It is of paramount importance to determine whether the thinning is accelerating. Our present theoretical understanding is not sufficient to firmly predict the future evolution of the Pine Island Glacier," he said.