Historic Survey of Earth’s Melting Land Ice aided by NASA Data

Making use of satellite data, allowing for accurate measurements from space, a team led by researchers at the University of Colorado at Boulder, have completed a historic survey of the ice melt occurring in the Earth’s polar regions. The results of which were published online in the February 8th edition of the journal Nature.

Using the data, collected over a 7 year period beginning in 2003 from NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE), the team has been able to assess how much the melting ice is adding to the global rise in sea level.

While the study encompassed all major global ice melting, much of the focus was on the glaciers and ice caps outside of Greenland and Antarctica. According to the research, the total global ice mass lost from Greenland, Antarctica and Earth’s glaciers and ice caps during the study period was about 4.3 trillion tons (1,000 cubic miles).

To give some perspective, this is enough ice, according to NASA, to cover the entire United States in a blanket of ice to a depth of about a foot and a half. This loss in ice resulted in an increase in sea level world-wide of about a half an inch or 12 millimeters in just 7 years.

“Earth is losing a huge amount of ice to the ocean annually, and these new results will help us answer important questions in terms of both sea rise and how the planet’s cold regions are responding to global change,” said University of Colorado Boulder physics professor John Wahr, who helped lead the study. “The strength of GRACE is it sees all the mass in the system, even though its resolution is not high enough to allow us to determine separate contributions from each individual glacier.”

Annually, about 385 billion tons (100 cubic miles) of ice loss from Greenland and Antarctica occur, according to the study, with another 148 billion tons (39 cubic miles) lost in other areas.

The observations from satellites have allowed the team to complete a much more comprehensive study than had been performed in previous decades relying only on ground based monitoring of a fraction of the glaciers measured by GRACE.

Their was one piece of good news resulting from the survey. The findings indicated that the ice loss in the Asian mountain ranges like the Himalaya, the Pamir and the Tien Shan was only about 4 billion tons of ice annually versus previous ground-based estimates of 50 billion tons annually.

“The GRACE results in this region really were a surprise,” said Wahr, who also is a fellow at the University of Colorado-headquartered Cooperative Institute for Research in Environmental Sciences. “One possible explanation is that previous estimates were based on measurements taken primarily from some of the lower, more accessible glaciers in Asia and extrapolated to infer the behavior of higher glaciers. But unlike the lower glaciers, most of the high glaciers are located in very cold environments and require greater amounts of atmospheric warming before local temperatures rise enough to cause significant melting. This makes it difficult to use low-elevation, ground-based measurements to estimate results from the entire system.”

“This study finds that the world’s small glaciers and ice caps in places like Alaska, South America and the Himalayas contribute about .02 inches per year to sea level rise,” said Tom Wagner, cryosphere program scientist at NASA Headquarters in Washington. “While this is lower than previous estimates, it confirms that ice is being lost from around the globe, with just a few areas in precarious balance. The results sharpen our view of land ice melting, which poses the biggest, most threatening factor in future sea level rise.”