Glaciers Contribute One Third to Sea Level Rise

Ninety-nine percent of all of Earth’s land ice is locked up in the massive Greenland and Antarctic ice sheets. However, over the period 2003 to 2009, the melting of the world’s other land ice stored in glaciers contributed just as much to sea level rise as the two ice sheets combined.
Image: Ben Marzeion

“In this international cooperation, we have been able to discern much more precisely than ever before how much these glaciers as a whole are contributing to sea level rise,” says Georg Kaser from the Institute for Meteorology and Geophysics of the University of Innsbruck about the study A Reconciled Estimate of Glacier Contributions to Sea Level Rise: 2003 to 2009. “The study confirms that the melting of these smaller ice bodies account for one third of the observed sea level rise while the ice-sheets and thermal expansion of the oceans account for two thirds,” says Kaser. “Previous estimates of the recent contribution of glaciers to sea level rise have differed widely.”
In the new study 16 researchers from 10 countries compared traditional ground measurements to satellite data from NASA’s ICESat (Ice, Cloud and land Elevation Satellite) and GRACE (Gravity Recovery and Climate Experiment) missions. In combination with an inventory of the world’s glaciers they have been able to come up with more precise mass change estimates for glaciers in all regions of the planet. “Estimates of glacier loss based only on traditional extrapolation of local field measurements over larger regions, like entire mountain ranges, with few observations can sometimes overestimate ice loss,” says Georg Kaser. “Even though the satellite methods have their own limitations, their estimates of mass change for large glacierized regions agree very well,” says glaciologist Georg Kaser. “With this tested mix of methods we took a big step forward towards more precise glacial ice mass loss estimates.”

Correction of previous estimates

The new research found that all glacierized regions lost mass from 2003 to 2009, with the biggest ice losses occurring in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas. In contrast, Antarctica’s peripheral glaciers – smaller ice bodies not connected to the main ice sheet – contributed little to sea level rise during that period. These findings differ considerably from previously published estimates for Antarctic glaciers for the period 1961 to 2004, which showed that they accounted for 30 % of the global mass loss of glaciers.
The findings, published in Science, have serious implications for past assessments. “We deduce from the new findings that we need to thoroughly reexamine past estimates of glacier contributions to sea level rise,” concludes Kaser.