Major glacier in Antarctica is shrinking

by Danielle Knight

Washington, 31 Jan 2001 (IPS) -- A major glacier formation in Antarctica is shrinking, according to a new scientific report, which is likely to heighten concerns that global warming is melting the world’s ice cover.

Scientists at the University College London and the British Antarctic Survey presented new evidence Thursday suggesting that the West Antarctica’s Pine Island Glacier is thinning at a rate that, if continued, will have the glacier afloat within 600 years.

Using satellite data, the scientists monitored the glacier between 1992 and 1999 and found that this inland glacier of the West Antarctic Ice Sheet lost about 31 cubic kilometres of ice during this time. The study appeared Thursday in the journal Science, a peer-reviewed publication.

The glacier is decreasing by approximately four gigatons per year, which is equivalent to approximately 0.01 millimetres of sea-level rise, says the report.

The Pine Island Glacier is the largest of all the ice streams that feed into the ocean and could therefore be a key indicator of any larger changes afoot in the ice sheet’s interior, according to the researchers.

Scientists have taken an interest in monitoring the West Antarctic Ice Sheet because it contains enough water to raise the global sea level by approximately five metres if the ice melted.

Andrew Shepherd, one of the scientists involved in the study, told IPS that there is no suggestion that the findings are a sign of global warming. “The cause of the thinning/retreat still remains a mystery,” he says.

But Shepherd says that the new data add “weight to the argument that changes at the ice sheet coastline, such as those that may occur due to global warming, can affect the interior of the ice sheet, where the majority of ice is stored”. He says that questions still remain about the speed at which the ice sheet is thinning. Scientists studying glaciers have debated for many years whether or not a retreat of the West Antarctic Ice Sheet would be an accelerating process.

“At present, our data show that the retreat has been uniform for the past eight years,” says Shepherd. If the retreat were to accelerate, the resulting increase in sea levels could be far greater and sooner than currently predicted.

Other scientific studies of the massive Antarctic ice cover, which represents 91% of the Earth’s ice, have also concluded that the ice is melting. But there is disagreement over how quickly this is happening.

One study published in Science in 1999 estimates that the Western Antarctic Ice Sheet, the smaller of the continent’s two ice sheets, has retreated at an average rate of 122 metres a year for the past 7,500 years and is in no danger of collapse.

But other studies suggest that the sheet may break more abruptly if melting accelerates. They point to signs of past collapse, as well as to fast-moving ice streams within the sheet that could speed ice melt.

The new findings published Thursday are likely to increase concerns that global warming, caused by the burning of oil, gas and coal, is having an impact on the Earth’s ice cover.

At an international conference in China on Jan. 22, an international panel of hundreds of scientists from more than 100 countries unanimously approved a report that confirmed that the evidence for humanity’s influences on the global climate is stronger than ever.

The Intergovernmental Panel on Climate Change predicts an average warming of 1.4 to 5.8 degrees Celsius over the coming century.  Scientists expect that this will cause more frequent and intense storms, droughts and floods. Sea levels are projected to rise by 0.09 to 0.88 metres from 1990 to 2100, according to the report.

The Panel concludes that it is very likely that snow cover has decreased by about 10% since the late 1960s in the mid- and high-latitudes of the Northern Hemisphere. It also says that it is likely that there has been a 40% decline in Arctic sea-ice thickness during late summer to early autumn in recent decades.

According to the Worldwatch Institute, an environmental think-tank here in Washington, scientists worldwide are witnessing a dramatic melting at the planet’s coldest regions. “From the polar regions to high mountain glaciers, Earth’s ice cover is melting at an astonishing rate,” says Lisa Mastny, a researcher at the Institute.

The World Glacier Monitoring Service in Switzerland says that the planet’s glaciers are now shrinking faster than they are growing and losses in 1997-1998 were “extreme”.

Scientists predict that up to a quarter of the global mountain glacier mass could disappear by 2050, and up to half by 2100 - leaving large patches only in Alaska, Patagonia, and the Himalayas.

Mastny says the disappearance of the Earth’s ice cover would significantly alter the global climate since ice reflects large amounts of solar energy back into space and helps cool the planet.

“When ice melts, however, this exposes land and water surfaces that retain heat - leading to even more melt and creating a feedback loop that accelerates the overall warming,” she says.