Greenland’s ice in motion…

Mark Cochrane seems to be joining the camp of concerned scientists who are worried about the escalating rate of melt in Greenland……  the problem with tipping points of course is that there is no data to show they are coming, and only become obvious in the rear vision mirror…… so here’s another guest post from mark, hot on the heels of Ocean acidification feedback causes increased warming

 

Regional warming in Greenland is not currently well incorporated into global climate models. The long and short of this being that the melting of the ice in Greenland is proceeding at a pace more rapid than are generally appreciated. A recent study (Khan et al. 2014) shows that, in addition to the known speed up of glacial streams in the west and southeast of Greenland, a monstrous ice stream in the northeast, 600 km long, that drains 16% of the Greenland ice has recently begun moving and accelerating in the last decade.

Figure 1 Changes in surface elevations obtained using ICESat, ATM, LVIS and ENVISAT data. Ice surface elevation change rates in m/yr

from April 2003 to April 2006 (a), April 2006 to April 2009 (b) and April 2009 to April 2012 (c). (sorry for the low quality figure – the original from the paper didn’t show up in the post even though it was on my screen!)

At the areas in yellow are dropping and the red one are dropping very fast. The average ice-sheet-wide loss from Greenland has increased from 172.4 (+/- 21.7 Gt/yr) during April 2003-2006 to 359.8 (+/- 28.9 Gt/yr) during April 2009-2012. This represents more than a doubling in the last 6 years.

Just how big is that? A single gigatonne of ice is a block 1km on a side.

That cubic kilometre of ice yields 1 billion cubic metres. The current melt rate from Greenland is about 360 GT/yr. To put that in some sort of perspective, Greenland is disgorging water at an equivalent of 70% of the Mississippi river flow rate, but with the rate in increased melting, it could likely be 1.5 times the Mississippi outflow by 2018.

The take home message is that sea levels will continue to rise faster than the current predictions.