Boffins: Antarctic glacier in irreversible decline, will raise sea levels by 1cm

Pine Island Glacier signal of watery things to come

A massive Antarctic glacier is in irreversible decline and will add up to a centimeter to world sea levels in the next 20 years, claim polar scientists.

A new paper in Nature Climate Change describes how the Pine Island Glacier (PIG) has been shedding ice into the ocean at a dramatically increasing rate. Using observations on the grounds and from satellites, the team says the rate of loss has increased from 20 gigatonnes a year between 1992 and 2011 to about 100 gigatonnes a year. The team estimates the rate of loss will continue at this rate for the foreseeable future.

As the PIG's flow into the sea increases, the grounding line – the point where the glacier leaves land and floats on the ocean – has retreated by tens of kilometres. This allows warming ocean currents to break off larger chunks of the glacier, increasing the speed with which it slides into the ocean.

"The result is a striking vision of the near future. All the models suggest that this recession will not stop, cannot be reversed and that more ice will be transferred into the ocean," said the paper's lead author Dr Gaël Durand of CNRS, Laboratoire de Glaciologie et de Géophysique de l'Environnement, at the University of Grenoble in France.

The PIG is just part of the West Antarctic Ice Sheet, which the scientists warn is also thinning. The sheet is formed by snow falling on Antarctica and being compressed by its own weight, but the recent paucity of snowfall means the glaciers flowing onto it have been steadily losing mass into the sea.

A team of scientists, led by the British Antarctic Survey, just traversed the entire PIG and mapped it using radar and seismic systems. It found the glacier is thinning at different rates, and encouragingly that between 2010 and 2012 PIG actually thickened slightly, something the team attribute to a La Niña event in the tropical Pacific. ®

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