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Record Melting ‘Not Undermining Greenland’s Ice Sheet’

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John Ross, The Australian

Scientists have found that record melting is not undermining Greenland’s massive ice sheet, reducing fears that it could literally slide into the ocean.

 

A study reported today in the Proceedings of the National Academy of Sciences has found the ice sheet moved more slowly than average in 2012, despite “unbelievably warm” temperatures that triggered the most extreme melting in 123 years.

The findings alleviate concerns that lubrication caused by meltwaters which sink to the base of the ice sheet could accelerate its flow into the ocean.

“It’s a bit like walking into a bathroom with a wet floor,” said co-author Matt King of the University of Tasmania. “All of a sudden you’re moving a lot faster than you intended to.”

He said the ice sheet flowed up to twice as quickly during warm summer periods such as July 12 last year, when 99 per cent of the ice sheet experienced some melting – the most widespread melt since 1889.

For the last decade scientists have speculated that this accelerated flow could exacerbate sea level rises caused by surface runoff and icebergs breaking away from the world’s second biggest ice sheet.

Professor King said 2012 was an ideal time to test the theory, because surface temperatures had reached levels considered likely to be commonplace by the end of the century. “It gave us a great opportunity to (see) how the ice sheet responds under those conditions,” he said.

The study used GPS to track the movement of poles sunk into a 120 kilometre strip of ice in south-western Greenland. It found that the total amount of ice flowing into the ocean in 2012 was 6 per cent less than in the “average” melt year of 2009.

The researchers reasoned that accelerated summer ice flows were “negated” by unusually slow flows during the winter, when the water at the base of the ice sheet could not build up enough pressure to maintain the momentum. “The summer isn’t the full story – you need to look at the whole year,” Professor King said.

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