Melting of ice sheets in Antarctica and Greenland is accelerating, according to a new study to be published this month in Geophysical Research Letters. According to the research, this acceleration is three times faster than what is being observed for mountain glaciers and ice caps.
From the study:
The magnitude of the acceleration suggests that ice sheets will be the dominant contributors to sea level rise in forthcoming decades, and will likely exceed the IPCC projections for the contribution of ice sheets to sea level rise in the 21st century.
According to the new research, if melting of ice sheets continues at the current rate for the next 40 years, sea level rise from that source alone would equal 15 centimeters, or 5.9 inches by the year 2050. With ice loss from glaciers, ice caps and thermal expansion of the oceans also factored in, sea level could come up by a total of 32 centimeters, or 12.6 inches, by mid-century, according to the new research.
There is a caveat:
The researchers say there are significant uncertainties inherent in their projections. Of course, that could well mean greater sea level rise than they project in their paper. In fact, with new research over the years, scientists have repeatedly had to revise their estimates of sea level rise upward.
The last assessment report of the Intergovernmental Panel on Climate Change is a case in point. Published in 2007, it said we could get up to 59 centimeters of sea level rise by 2100. But that prediction did not include growing understanding of ice dynamics in Greenland. As a result, researchers have since estimated that sea level rise could exceed 1 meter by the end of the century. (For more information about this, see my post, “Mass Loss from Greenland Ice Sheet Accelerates,” from back in October.)
Even 1 meter of sea level rise would pose a major challenge. To offer one example, with a storm surge from a hurricane, New York City could actually be looking at 1.5 meters of water sloshing ashore. And that could flood a good portion of the city.
In the graphic at left, from the new research to be published in GRL, the the amount of ice lost from the Greenland and Antarctic ice sheets combined is plotted for the years 1992 through 2009. The graph is based on two independent measurement techniques, and the downward trend is clear.
So is the agreement between the two techniques. The first involved monitoring of ice sheets by synthetic aperture radar to determine ice loss, as well as climate modeling to determine additions to the ice sheets. The second used data from the Gravity Recovery and Climate Experiment (Grace) satellites. These spacecraft actually detect tiny changes in Earth’s gravity caused by alterations in the distribution of mass on our planet — including the movement of ice.
“These are two totally independent techniques, so it is a major achievement that the results agree so well,” co-author Isabella Velicogna of NASA’s Jet Propulsion Laboratory is quoted as saying in an American Geophysical Union press release, issued today.