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Melting glaciers

Satellite measurements show billions of tons of ice melting annually

An aerial view of a white glacier curving through mountains.

Alaska's Ruth Glacier in Denali National Park. (©UCAR.)

A study published in Nature that provides the first comprehensive satellite analysis of Earth’s melting glaciers and ice caps has grave implications for sea level rise.

The total global ice mass lost from Greenland, Antarctica, and the rest of Earth's glaciers and ice caps during the period 2003-2010 was about 4.3 trillion tons (1,000 cubic miles), contributing about 0.5 inches (12 millimeters) to global sea levels. The loss amount is roughly eight times the water volume of Lake Erie, or enough to cover the United States in 1.5 feet (.5 meter) of water, the authors note.

Historically, estimates of glaciers and ice caps have been made using ground-based measurements from Earth’s small number of monitored glaciers and extrapolating those measurements to other glaciers. The research team, which was led by the University of Colorado Boulder and includes NCAR scientist Sean Swenson, used satellite measurements from GRACE (Gravity Recovery and Climate Experiment) for the new study. These twin satellites circle Earth 16 times per day, quantifying changes in Earth’s gravity field caused by regional changes in the planet’s mass, including ice sheets and glaciers.

The study focused especially on glaciers and ice caps outside of Greenland and Antarctica.  About a quarter of the average annual ice loss during 2003-2010 came from these sources (roughly 148 billion tons, or 39 cubic miles), according to the results. Greenland and Antarctica, along with their peripheral glaciers and ice caps, shed about 385 billion tons (100 cubic miles) a year.

The research is especially important for its potential to help scientists better understand the processes behind sea level rise and how the planet’s cold regions are responding to climate change.

Thomas Jacob, John Wahr, W. Tad Pfeffer, Sean Swenson, “Recent contributions of glaciers and ice caps to sea level rise,” Nature, 2012; DOI: 10.1038/nature10847