Research published in the journal Science late last week confirms that melting of the Greenland ice sheet has accelerated in recent years, and is contributing to seal level rise.
An average 273 gigatons of ice has melted away annually between 2006 to 2008, leading to three-hundredths of an inch of sea level rise, an increase of more the 60 percent over the average ice loss between 2000 and 2008. The data indicates an acceleration of ice loss in recent years, due in part to the unusually warm summers says lead researcher Michiel van den Broeke, a specialist in polar meteorology at Ultecht University.
The study used two independent sources of satellite observations to make the yearly measurements, combining the data with computer models to assist in better understanding the nature of the ice loss. The models tracked with the observed data, allowing scientists to use the models to help explain not only how much but also how the ice is diminishing. The modeling revealed two separate process at work on the ice: rising temperature, particularly during the three summers from 2006 to 2008, melting the surface of the ice sheet, and a quickening slide of glacial ice into the sea.
It is clear from these results that mass loss from Greenland has been accelerating since the late 1990s,” said study co-author Professor Jonathan Bamber from the University of Bristol. “The underlying causes suggest this trend is likely to continue in the near future.” he said. “We have produced agreement between two totally independent estimates, giving us a lot of confidence in the numbers.”
If the rate of acceleration measured over the past few years continues, the Greenland ice sheet could cause a sea level rise of 40 centimeters by the end of the century, irrespective of other global factors that contribute to rising seas. A “best case scenario” with ice melting at a steady pace indicates an 18 centimeter rise in sea level (that’s about 7 to nearly 16 inches).
Weather or climate?
Scientists welcomed the study as “timely and important,” but also cautioned that the research covers a particularly short time period, making it hard as yet to discern if the measurable acceleration of ice melt between 2006 and 2008 is part of the long-term trend.
Weather – an unusually cold year, or an unusually hot year – really does exist, and will exist in the future,” said glaciologist Richard Alley. “A trend of a few years can be influenced by such weather.”