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This animation shows dramatic changes in Greenland's ice mass from 2003 through 2011. Created with data from NASA's Gravity Recovery and Climate Experiment (GRACE), it reveals how much ice has been lost and gained each year. It provides striking visible evidence that Greenland has been losing large amounts of water into the ocean as surface ice melts and glaciers discharge more ice into the sea.
NASA launched GRACE in 2002 to obtain high-resolution, global measurements of Earth's gravity field from space. After 10 years, GRACE continues to reveal increasingly subtle changes in Earth's gravity field. These gravity variations reflect changes in the distribution of Earth's mass, including changes in water storage in river basins on land, changes in ice mass in Greenland and Antarctica, ocean mass changes, and even changes caused by large earthquakes. GRACE data are substantially improving our knowledge of important aspects of global change, including the climate consequences of a warming world.
As GRACE's twin satellites pass over features on Earth, the distance between the satellites changes ever so slightly in response to the mass of these features. Extremely sensitive instruments on GRACE can measure changes in the distance between the twin satellites to an accuracy of 1 micrometer (one-millionth of a meter), which is 20 to 100 times smaller than the width of a human hair. As GRACE orbits, it provides data for scientists to construct a new map of Earth's gravity field every month.
Grace is a collaborative endeavor involving the Center for Space Research at the University of Texas, Austin; NASA's Jet Propulsion Laboratory, Pasadena, Calif.; the German Space Agency and Germany's National Research Center for Geosciences, Potsdam.