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Tuesday, November 20, 2007

Greenland Ice Sheet, Glaciers 2007

Shockwaves from melting icecaps are triggering earthquakes, say scientists

By Daniel Howden, in Ilulissat, Greenland

Published: 08 September 2007, The Independent

High up inside the Arctic circle the melting of Greenland's ice sheet has accelerated so dramatically that it is triggering earthquakes for the first time.

Scientists monitoring the glaciers have revealed that movements of gigantic pieces of ice are creating shockwaves that register up to three on the Richter scale.

The speed of the arctic ice melt has accelerated to such an extent that a UN report issued earlier this year is now thought to be out of date by its own authors.

The American polar expert Robert Correll, among the key contributors to the UN International Panel on Climate Change (IPCC) report issued in February, described the acceleration as "massive".

Estimates of the likely rise in sea levels this century vary, and the IPCC published a conservative range of between 20cm-60cm. But those estimates are now heavily disputed, with many scientists insisting that new data collected since the IPCC report suggested a rise closer to two metres. Professor Correll said there was now a "consensus" that a significant acceleration in the loss of ice mass has occurred since the last report.

The revelations came at a conference in the north of Greenland, which has drawn world religious leaders, scientists and environmentalists to the Ilulissat Icefjord. Ilulissat is home to the most active glacier in Greenland and it was one of the immense icebergs that calve from it on a daily basis that is believed to have sunk the Titanic. The Arctic is acknowledged as the fastest warming place on earth.

The local Inuit population, whose lives have been drastically altered by the changing climate, were yesterday led in a silent prayer for the future of the planet by the Ecumenical Patriarch Bartholomew, the organiser of the arctic symposium and spiritual leader of the world's 250 million Orthodox Christians.

Greenland's ice cap is immense, the second largest in the world, and its break-up would be catastrophic. The packed ice is up to two miles thick and its total collapse into the ocean would raise worldside sea levels by seven metres.

At the Ilulissat Icefjord, 250km north of the Arctic Circle, the advance of the glacier into the sea is now visible to the naked eye. "It's moving toward the sea at a rate of two metres an hour," said Professor Correll. "It's exuding like toothpaste, moving towards us at 15 kilometres per year."

One day's worth of the Ilulissat ice would provide enough fresh water to supply the largest cities in the world for a whole year – and yet it amounts to only 7 per cent of Greenland's total melt.

As the glaciers thaw, pools of water are forming, feeding fractures in the ice, down which the water flows until it hits the bedrock.

"These so-called moulins are phenomenal," said Professor Correll, who said they had been remarkably scarce when he first visited the glacier in 1968. "Now they are like rivers 10 or 15 metres in diameter and there are thousands of them."

He compared the process to putting oil underneath the ice to make it move forward faster.

As the reality of the unprecedented thaw becomes apparent, the consequences are outstripping the capacity of scientific models to predict it.

Earthquakes, or glacial ice quakes, in the north-west of Greenland are among the latest ominous signs that an unprecedented step change is under way. The Finnish scientist Veli Albert Kallio is one of the region's leading ice experts and has been tracking the earthquakes.

"Glacial earthquakes in north-west Greenland did not exist until three years ago," he said.

The accelerating thaw and the earthquakes are intimately connected, according to Mr Kallio, as immense slabs of ice are sheared from the bed rock by melt water. Those blocks of ice, often more than 800m deep and 1500m long, contain immense rocks as well and move against geological faults with seismic consequences. The study of these ice quakes is still in its infancy, according to Professor Correll, but their occurrence is in itself disturbing. "It is becoming a lot more volatile," said Mr Vallio. Predictions made by the Arctic Council, a working group of regional scientists, have been hopelessly overrun by the extent of the thaw. "Five years ago we made models predicting how much ice would melt and when," said Mr Vallio. "Five years later we are already at the levels predicted for 2040, in a year's time we'll be at 2050."

This dramatic warming is being felt across the Arctic region. In Alaska, earthquakes are rocking the seabed as tectonic plates – subdued for centuries by the weight of the glaciers on top of them – are now moving against each other again.

In the north of Sweden, mean temperatures have risen above zero for the first time on record.

Professor Terry Callaghan has been working in the remote north of the country at a research station which has been taking continuous readings for the past 100 years. His recent findings tally with the accelerating pace of change elsewhere.

"Mean temperatures have remained below zero here since medieval times," said Professor Callaghan. "Now, over the past 10 years we have exceeded zero, the mark at which ice turns to water." Professor Correll said: "We are looking at a very different planet than the one we are used to."

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