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Global effects of rapid thaw of Greenland’s permafrost

Greenland: How rapid climate change on world’s largest island will affect us all The ice sheet is melting and permafrost is thawing. What’s happening in Greenland will speed up climate change across the world, The Independent, 7 Sept 17, Kathryn Adamson 

 The largest wildfire ever recorded in Greenland was recently spotted close to the west coast town of Sisimiut, not far from Disko Island where I research retreating glaciers. The fire has captured public and scientific interest not just because its size and location came as a surprise, but because it is yet another sign of deep environmental change in the Arctic.

Greenland is an important cog in the global climate system. The ice sheet, which covers 80 per cent of the island, reflects so much of the sun’s energy back into space that it moderates temperatures through what is known as the “albedo effect”. And since it occupies a strategic position in the North Atlantic, its meltwater tempers ocean circulation patterns.

But Greenland is especially vulnerable to climate change, as Arctic air temperatures are currently rising at twice the global average rate. Environmental conditions are frequently setting new records: “the warmest”, “the wettest”, “the driest”.

Despite its size, the fire itself represents only a snapshot of Greenland’s fire history. It alone cannot tell us about wider Arctic climate change.

But when we superimpose these extraordinary events onto longer-term environmental records, we can see important trends emerging.

The ice sheet is melting

Between 2002 and 2016 the ice sheet lost mass at a rate of around 269 gigatonnes per year. One gigatonne is one billion tonnes. One tonne is about the weight of a walrus.

During the same period, the ice sheet also showed some unusual short-term behaviour. The 2012 melt season was especially intense – 97 per cent of the ice sheet experienced surface melt at some point during the year. Snow even melted at its summit, the highest point in the centre of the island where the ice is piled up more than 3km above sea level………

In Greenland, like much of the Arctic, rising temperatures are thawing the permafrost. This means the active layer is growing by up to 1.5cm per year. This trend is expected to continue, seeing as under current IPCC predictions, Arctic air temperatures will rise by between 2.0°C and 7.5°C this century.

Arctic permafrost contains more than 1,500 billion tonnes of dead plants and animals (around 1,500 billion walrus equivalent) which we call “organic matter”. Right now, this stuff has been frozen for thousands of years. But when the permafrost thaws this organic matter will decay, releasing carbon and methane (another greenhouse gas) into the atmosphere.

If thawing continues, it’s estimated that by 2100 permafrost will emit 850-1,400 billion tonnes of CO₂ equivalent (for comparison: total global emissions in 2012 was 54 billion tonnes of CO₂ equivalent). All that extra methane and carbon, of course, has  the potential to enhance global warming even further……..http://www.independent.co.uk/environment/greenland-how-rapid-climate-change-on-worlds-largest-island-will-affect-us-all-a7926006.html

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September 9, 2017 - Posted by | ARCTIC, climate change

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