Saturday, January 22, 2011
The chilly fact is that the Greenland ice cap is melting at an accelerated rate. The big melt achieved a new record in 2010 according to new research.
"This past melt season was exceptional, with melting in some areas stretching up to 50 days longer than average," said Dr. Marco Tedesco, Director of the Cryosphere Processes Laboratory at the City College of New York (CCNY - CUNY), who is leading a project studying variables that affect ice sheet melting. "Melting in 2010 started exceptionally early at the end of April and ended quite late in mid- September."
Nuuk, the capital of Greenland has 'sweltered' through the warmest spring and summer since records began in 1873.
During 2010 summer temperatures up to 3°C above the average were combined with reduced snowfall to increase the ice melt. Bare ice was exposed earlier than the average and longer than previous years, contributing to the extreme record.
"Bare ice is much darker than snow and absorbs more solar radiation," said Dr Tedesco. "This means the old ice is warming, melting, and running off into the sea."
"Other ice melting feedback loops that we are examining include the impact of lakes on the glacial surface, of dust and soot deposited over the ice sheet and how surface melt water affects the flow of the ice toward the ocean."
The accelerated melting was more than twice the average annual loss in Greenland over the previous three decades, surpassing a record set in 2007, and will be a major driver of sea level rise this century, expected to be about 1 metre by 2100.
There is about 7 metres of sea level rise locked up in the Greenland ice sheet. If we allow temperatures to rise beyond 2 degrees Celsius there is a greater than 50 per cent chance that the Greenland ice sheet will disintegrate over the next 300-1000 years.
But even if we stop all emissions now, substantial melting from Greenland should be expected with two metres of sea level rise inevitable at this point, according to sea level rise expert Stefam Rahmstorf from the Potsdam Institute.
While a one metre sea level rise by 2100 is now seen by many scientists as well within the range of possibilities given current emission trends, James Hansen in a draft paper (Jan 2011) says that "[Business as usual] scenarios result in global warming on the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain."
Indeed, there has just been a major grant award of GBP3.3 million over five years from the UK's Natural Environment Research Council (NERC) to a Southampton-led consortium project to study past and possible future sea-level rise.
"The vulnerability of extensive near-coastal habitation, infrastructure, and trade makes global sea-level rise a major concern for society," said project coordinator Professor Eelco Rohling of the University of Southampton's School of Ocean and Earth Science (SOES) based at the National Oceanography Centre, Southampton. "By studying how sea level responded during the warmer periods between ice ages, we hope to obtain a better picture of how much and how quickly sea level may rise as a result of global warming."
The Greenland study received sponsorship from WWF, the US National Science Foundation (NSF) and NASA. It examined surface temperature anomalies over the Greenland ice sheet surface, as well as estimates of surface melting from satellite data, ground observations and models. The study was published in Environmental Research Letters.
WWF climate specialist Dr. Martin Sommerkorn commented "Sea level rise is expected to top one metre by 2100, largely due to melting from ice sheets. And it will not stop there - the longer we take to limit greenhouse gas production, the more melting and water level rise will continue."
Greenland Melting Video from Cryospheric Processes and Remote Sensing Laboratory, NYC.
* Story adapted from media release - New melt record for Greenland ice sheet
* Photographs and other media materials can be accessed on greenland.cryocity.org
* Dr. Tedesco's continuing research on ice sheets can be followed on www.cryocity.org
* For more on Arctic climate change, visit http://www.panda.org/arctic.
Related blog articles:
* Arctic climate warming at unprecedented rate due to Global Warming - Oct 2010
* Arctic Sea Ice heading for Rapid Disintegration: Greenland Ice Sheet melting - Oct 2007
* Greenland Ice Sheet melting faster than expected - Jan 2006
* Carbon Dioxide Emissions cause Arctic to Melt, Sea Levels to Rise Nov 2004
* Climate Meltdown: Greenland ice cap to raise sea levels - April 2004