Sea ice disappearing faster than predicted

Without the cap's white brilliance to reflect sunlight, the region would heat up even more. Photo / AP

Sea ice in the Arctic is disappearing at a far greater rate than previously expected, according to data from a satellite launched to study the thickness of Earth's polar caps.

Preliminary results from the European Space Agency CryoSat-2 probe indicate that 900cu km of summer sea ice has disappeared from the Arctic ocean over the past year.

This rate of loss is 50 per cent higher than most scenarios outlined by polar scientists and suggests that global warming, triggered by rising greenhouse gas emissions, is beginning to have a major impact on the region. In a few years the Arctic ocean could be free of ice in summer, triggering a rush to exploit its fisheries, oil, minerals and sea routes.

Using instruments on earlier satellites, scientists could see the area covered by summer sea ice in the Arctic had been dwindling rapidly. But the new data indicate this ice has been thinning dramatically at the same time.

For example, in regions north of Canada and Greenland, where ice thickness regularly stayed at around 5-6m in summer a decade ago, levels have dropped to 1-3m.

"Preliminary analysis of our data indicates that the rate of loss of sea ice volume in summer in the Arctic may be far larger than we had previously suspected," said Dr Seymour Laxon, of the Centre for Polar Observation and Modelling at University College London (UCL), where CyroSat-2 data is being analysed.

"Very soon we may experience the iconic moment when, one day in the summer, we look at satellite images and see no sea ice coverage in the Arctic, just open water."

The consequences of losing the Arctic's ice coverage, even for only part of the year, could certainly be profound. Without the cap's white brilliance to reflect sunlight back into space, the region will heat up even more than it is doing so at present. As a result, ocean temperatures will rise and methane deposits on the ocean floor could melt, evaporate and bubble into the atmosphere. Scientists have recently reported evidence that methane plumes are now appearing in many areas.

Methane is a particularly powerful greenhouse gas and rising levels of it in the atmosphere are only like to accelerate global warming. Greenland's glaciers could melt faster and raise sea levels even more rapidly than they are at present. "With the temperature gradient between the Arctic and equator dropping, as is happening now, it is also possible that the jet stream in the upper atmosphere could become more unstable," added Professor Chris Rapley of UCL.

"That could mean increasing volatility in weather in lower latitudes, similar to that experienced this year."

CryoSat-2 is the world's first satellite to be built specifically to study sea-ice thickness and was launched, on a Dniepr rocket from Baikonur cosmodrome, Kazakhstan, on April 8, 2010. Previous Earth monitoring satellites had mapped the extent of sea-ice coverage in the Arctic.

However, the thickness of that ice proved more difficult to measure.

- Observer