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Minggu, 06 September 2009

Arctic Meltdown

The settlement of Tasilaq in Greenland where the Arctic Sunrise  stopped to re-supply for its expedition.

The settlement of Tasilaq in Greenland where the Arctic Sunrise stopped to re-supply.

Sermilik Fjord, Greenland — A climate tipping point is looming closer every day in the Arctic. The more we find out about the Polar Regions, the more we realise that what we know about the impact of feedback effects has been underestimated. Recent discoveries highlight the need for action now, before it’s too late.

Subtropical currents

A team of independent scientists on board the Arctic Sunrise is investigating whether warming subtropical ocean currents are causing Greenland glaciers to melt faster than before.

While the melt from warming temperatures is a known phenomenon, the influence of currents is less understood, and new research conducted by Dr Fiamma Straneo of the Woods Hole Oceanographic institution is groundbreaking. (Or, perhaps, "icebreaking"?)

"Over the last decade we've seen dramatic changes in the Greenland ice sheet; in particular there’s been a large loss of mass of ice from Greenland’s outlet glaciers. One of the mechanisms we think may have triggered these changes is the inflow of warm subtropical water inside of Greenland's glacial fjords," Dr Straneo said.

A (frozen) river runs through it

These currents could be causing the dramatic melt of Greenlandic glaciers. Dr Gordon Hamilton, of the University of Maine, has been studying the speed of flow of the Greenland glaciers, and in particular Helheim glacier.

Glaciers are like frozen rivers, with ice slowly moving downstream at an average of 50 meters per year. Helheim glacier is moving at the speed of 25 meters per DAY. Located further North, the Kangerdlugssuaq glacier moves at an average of 38 meters per day. This is opening the way for the Greenland ice sheet to flow out, melt in the Atlantic Ocean, and contribute to sea level rise.

"Kangerdlugssuaq Glacier is probably the world's fastest moving glacier. It tripled its speed between 2004 and 2005, which tells us the glacier is moving mass out of the middle of Greenland's ice sheet, in the form of icebergs, at a rate three times faster than just a few years ago. This has important implications for both the mass balance of the Greenland ice sheet, and for the rate of global sea level rise," said Dr Hamilton.

Accelerating feedback effects

Other feedback effects in the Arctic are highlighted in a new WWF report, pointing out that their influence on the global climate also may have been underestimated.

Arctic multi-year sea ice is increasingly replaced by younger sea ice, making the ice-cap more vulnerable to melting in the summer. This allows the surface water to absorb more heat. The permafrost (permanently frozen ground) is heating up as well, releasing underground methane, a potent greenhouse gas. This methane then further contributes to global warming.

This report also points out that the International Panel on Climate Change's (IPCC) 2007 estimates on sea-level rise were too optimistic, and offers new estimates of up to 1.2 meters by the end of the century.

Beyond the tipping point

In 2007, the IPCC reported an estimated sea-level rise of 20 to 50 cm. As worrying as these figures were, evidence now suggest things are worse than they'd thought. The effect that the melting Greenland ice-sheet could have on sea-level rise was not fully included in the IPCC reports, since these findings are too recent.

Once we go beyond the tipping point where global warming feeds itself, there will be no going back. The time for action is now. In 95 days, the Copenhagen climate Conference will start. World leaders have to show their commitment to the climate by attending and adopting strong emissions targets.

We can wait no longer.


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