Friday, April 3, 2009

Arctic summer may be ice-free in 30 years

New studies show floating sea ice more vulnerable to sudden melting

By Steve Connor, Science editor

The Indedependent, Saturday, 4 April 2009

The frozen ocean of the Arctic might disappear far sooner than scientists have previously predicted with the first ice-free summer occurring within the next 30 years – three times earlier than estimated.

A study of computer models of the Arctic region has found that the vast expanse of floating sea ice that covers the region is far more vulnerable to rapid melting than earlier studies had assumed. The latest analysis found that virtually all the sea ice in the Arctic will have melted during the summer months by 2037, and that it may even disappear as soon as the summer of 2020. Previous studies had suggested that this was unlikely to happen until at least the end of the century.

An ice-free Arctic would spell disaster for the polar bear which uses the summer ice pack to hunt seals. It could also increase regional temperatures because open ocean absorbs more heat from sunlight than the reflective surface of the sea ice.

The latest study was carried out by scientists from the US National Oceanic and Atmospheric Administration (NOAA) and the University of Washington in Seattle using the six most sensitive computer models of the Arctic region.

The findings, published in the journal Geophysical Research Letters, found that the ice cover was likely to melt rapidly in the next couple of decades, culminating in an open sea, except for a band of ice bordering the shores of northern Canada and Greenland.

"The Arctic is changing faster than anticipated. It's a combination of natural variability, along with warmer air and sea conditions caused by increased greenhouse gases," said James Overland of NOAA, who carried out the research. The scientists estimate that by the end of summer 2037 there will be about 1 million square kilometres (about 620,000 square miles) of sea ice left in the Arctic region, compared with the 4.6 million square kilometres (2.8 million square miles) today.

Much of the remaining ice is likely to be blown by the prevailing winds against the shorelines of Canada and Greenland where it will be forced into thick layers that could remain frozen despite the increasing temperatures.

Much of the ocean will become easy to navigate in summer, raising the prospect of the exploration of the sea bed for its wealth of minerals and oil. "But it could also cause an eco–system upheaval," a spokesman for the NOAA said. The six models used by the NOAA scientists were taken from 23 analysed by scientists from the Intergovernmental Panel on Climate Change, who predicted a slower melting rate for the Arctic sea ice. All six showed that once the ice at the end of the summer melting period drops to 4.6 million square kilometres, there is a rapid increase in the rate of further melting.

Scientists fear that this "tipping point" may already have been reached given that in 2007 the summer sea ice fell to an all-time record of 4.3 million square kilometres, and in 2008 it reached 4.7 million square kilometres – the second lowest on record.

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