NASA mission calculates global ice melt and rising sea levels

GRACE on orbit

(Credit: NASA)

From 2003 to 2010, NASA satellites systematically measured all of Earth's melting glacial ice--the results added up to 4.3 trillion tons of water and a global sea level rise of half an inch.

Put in perspective, that's enough ice to bury the entire U.S. 1.5-feet deep.

These calculations are detailed in a new study released today by a team of scientists at the University of Colorado. The scientists used satellite measurements from the NASA Gravity Recovery and Climate Experiment (GRACE), which launched in 2002 and focused on how melting ice from glaciers and ice caps is adding to global sea level rise.

"Earth is losing a huge amount of ice to the ocean annually," said professor John Wahr, who helped lead the study. "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."

Of all of the ice loss measured yearly, around one quarter came from glaciers and ice caps outside of Greenland and Antarctica, which equaled about 148 billion tons or 39 cubic miles, according to the study. Melting ice from Greenland, Antarctica, and nearby caps and glaciers averaged roughly 385 billion tons, or 100 cubic miles, per year.

This study is groundbreaking because it is the first time that all of the nearly 200,000 glaciers worldwide have been monitored together for an extended amount of time. Typically, estimates have been made on just a few glaciers and then the results are applied to other glaciers that have not yet been monitored.

Some of the study's results are unexpected, such as the ice melt in Asia's Himalayan, Pamir, and Tien Shan mountain ranges. Previously estimates were as high as 50 billion tons of ice loss a year in the three ranges combined, but calculations from GRACE put it closer to 4 billion tons annually.

"The GRACE results in this region really were a surprise," Wahr said. "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."

Although some of the findings in this study are lower than prior estimates, NASA warns that melting glacial ice and sea level rise are still a deep concern regarding climate change.

"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 NASA scientist Tom Wagner. "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."