Arctic Ice Sheets Are Cracking

Ocean contributing to melt

“Arctic Ice is cracking up. It has become very clear over the past five years that these sheets are not losing most of their mass through melting. They are losing it because the ice is flowing into the ocean faster than the snow is replacing it” said Duncan Wingham from University College London.

The bases of the glaciers seem to be slipping more easily over the rock than in the past, so they slide into the sea faster… it is possible that melting ice at the surface is boring holes through the ice sheets and lubricating their base.

Global warming might be speeding up this process.

Duncan Wingham and Andrew Shepherd from the University of Edinburgh, UK, have found that four glaciers retreating in unison are all in direct contract with the sea. This mans that relatively small changes in sea temperature could have a disproportionate effect on ice loss.

“Our assessment confirms that just one type of glacier in Antarctica is retreating today – those that are seated in deep submarine basins and flow directly into the oceans,” says Shepherd. These glaciers are vulnerable to small changes in ocean temperature, such as those that have occurred over the 20^th century and those predicted for the 21^st century. A rise of less than 0.5^oC could have triggered the present imbalance.”

(“What’s behind the big meltdown?”, New Scientist Vol 2591 24^th March 2007 pp 16,17)

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