American Geophysical Union meeting, San Francisco –
News from the Arctic just continues to get worse. A fair number of presentations here have been dealing with the dire 2007 conditions for sea ice and the Greenland ice sheet.
First up, Greenland. Last summer, more ice melted atop Greenland than ever before measured, adding to a consistent downward trend of some 135 gigatons of ice disappearing per year. Marco Tedesco, of the Goddard Space Flight Center in Maryland, told the meeting that surface temperatures in Greenland were four to six degrees Celsius warmer than usual this summer, which helped accelerate melting, particularly at high latitudes.
The situation is even more precarious for sea ice. A couple of researchers here have been tossing around dates like 2012 or 2014 for estimates of when the Arctic might be completely ice-free in summer. While these sorts of numbers are pretty arm-waving at the moment (numbers like 2040 were previously considered to be aggressive), there’s little reason to think the situation will get better in the next couple of years. Mark Serreze, of the University of Colorado, spent a keynote lecture on Tuesday showing images of Arctic ice shrinking like a snowman left out too long in the sun. In September of this year, sea ice covered just 4.2 million square kilometers – by far the lowest record ever.
And the ice isn’t only shrinking in extent – it’s also thinning. Don Perovich, of a US army cold regions and research laboratory in New Hampshire, reported on a single but extraordinary ice buoy in the Beaufort Sea. In June the buoy measured sea ice at that location as 3.3 metres thick – “really a healthy piece of ice,” as he put it. But by the end of the summer, 70 centimetres had melted off the top – and 2.2 metres (yes, metres) off the bottom.
When you see those dramatic maps of the Arctic ice extent shrinking over time, don’t forget that it’s also thinning – a complicating factor that may just make things worse in summers to come.
Cross-posted from Alex Witze on In the Field