Shrinking glaciers behind a third of sea-level rise

Water from the world's shrinking glaciers was responsible for almost a third of the rise in sea levels between 2003 and 2009, new research showed Thursday. A study published in the journal Science revealed that researchers had analyzed data gleaned from two NASA satellites as well as traditional ground measurements from glaciers around the world. "For the first time, we've been able to very precisely constrain how much these glaciers as a whole are contributing to sea rise," said Alex Gardner, assistant geography professor at Clark University in Worcester, Massachusetts. "These smaller ice bodies are currently losing about as much mass as the ice sheets." The most significant ice losses occurred in Arctic Canada, Alaska, coastal Greenland, the southern Andes and the Himalayas, the study found. The glaciers outside of the Greenland and Antarctic sheets lost an average of roughly 260 billion metric tons of ice annually during the period, leading to a rise in ocean levels of about 0.03 inches (0.7 millimeters) per year. "Because the global glacier ice mass is relatively small in comparison with the huge ice sheets covering Greenland and Antarctica, people tend to not worry about it," said Tad Pfeffer, a glaciologist of the University of Colorado at Boulder. "But it's like a little bucket with a huge hole in the bottom: it may not last for very long, just a century or two, but while there's ice in those glaciers, it's a major contributor to sea level rise." Scientists estimate that if all the glaciers in the world were to melt, sea levels would rise by about two feet. However if the entire ice sheet of Greenland were to vanish, the oceans would surge by 20 feet (0.6 meters). If the Antarctic lost its ice cover, levels would rise 200 feet. The study used data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, and the Gravity Recovery and Climate Experiment, or GRACE. ICESat, which ceased operation in 2009, tracked glacier changes by bouncing laser pulses off the surface to calculate the shifting height of ice cover. The GRACE system works by monitoring variations in Earth's gravity field caused by shifts in the planet's mass distribution, including displacements of ice.