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Vanishing glaciers: Antarctica's big melt

Leigh Dayton, Science writer
April 23, 2005

GLACIERS along the Antarctic Peninsula are retreating at an increasingly rapid pace and almost 90 per cent have melted significantly in the past 50 years.

The vanishing glaciers heighten concern about the impact of global warming, a team of US and British scientists claims.

They warn that if the glaciers continue to melt, the rate of rising sea levels will escalate, with dramatic consequences for island nations.

The researchers, with the British Antarctic and US Geological Surveys, conducted the first comprehensive survey of the peninsula's 244 "marine" glaciers, those flowing from the mountains to the sea. They used data covering the past 61 years.

In the journal Science yesterday, the group reported that 87 per cent of the glaciers they studied had retreated an average of 600m.

The retreat began 50 years ago at the warmer northern tip of the peninsula, then moved south as atmospheric temperatures rose by more than 2.5C along the peninsula.

"The widespread retreat of the glaciers on the Antarctic Peninsula was largely caused by climate change," said British team member glaciologist David Vaughan.

"Are humans responsible? We can't say for sure, but we're one step closer to answering this important question."

While global warming was critical, the researchers said it was not the only cause of the big melt. The peninsula's glaciers were also affected by factors such as ocean temperature and the movement of ocean currents.

The team leader, Britain's Alison Cook, said that 50 years ago most of the glaciers were slowly growing in length.

"But since then this pattern has reversed," she said. "In the last five years the majority were actually shrinking rapidly."

The fastest shrinker in any five-year interval was Widdowson Glacier on the west coast of the peninsula, close to the Antarctic Circle. It retreated 1.1km a year.

Sjogren Glacier, at the northern tip of the peninsula, has retreated 13km since 1993, more than any other glacier in the study.

Professor Michael Stoddart, the Australian Antarctic Program's chief scientist, said the glacier survey showed that "change is happening" in Antarctica. He said it complemented recent work by AAP scientists in the eastern Antarctic. There they found that sea ice -- ice freezing on the sea surface -- had melted over the past 50 years. The amount was yet to be tallied.

Researchers have also found that warming is affecting sub-Antarctic islands such as Heard and McDonald islands.

Increased temperatures on Heard Island, for example, have triggered glacial retreat, resulting in the formation of lagoons and freshwater lakes that have attracted new plants and animals.

On the peninsula, tufts of hardy grass have spread into lawns, scientists have observed.

To tease out the trends along the peninsula, Dr Cook and her colleagues compiled a record of the behaviour of the marine glaciers over time, based on 2000 aerial photographs, historic records and more than 100 satellite images.

Dr Cook then created three cartographic-quality maps that will soon be available around the world.

© The Australian (emphasis added)

http://www.theaustralian.news.com.au/common/story_page/0,5744,15057664%255E2702,00.html

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