[[VIDEO.PLAYER||West Antarctic Collapse||NASA JPL-UC Irvine glaciologist Eric Rignot explains how glaciers in West Antarctica are changing. Most glaciers in West Antarctica sit on a bed that is below sea level. The massive ice sheet’s exposure to ocean water makes it inherently unstable, a fact that scientists have warned about for decades. In recent years, scientists have observed the glaciers that flow into West Antarctica's Amundsen Sea are shedding ice at a faster rate. Now, new research shows there is nothing to stop these glaciers from being lost to the ocean—an event that will likely take centuries to unfold, but raise global sea level by four feet.||/system/video_items/18_RunawayGlaciers-540-MASTER_high.mp4||undefined||undefined||/system/resources/detail_files/24_still2_unstoppable0603_1920x1080.jpg||NASA JPL-UC Irvine glaciologist Eric Rignot explains how glaciers in West Antarctica are changing. ||Column-width||24||false||false]]

"GRACE has revolutionized our ability to determine how much glaciers and ice sheets are contributing to sea level rise and gives insight into how they will respond to future changes in atmosphere and ocean."

Alex S. Gardner, research scientist and member of NASA's Sea Level Change Team

GRACE data provide important information about the amount of sea level rise caused by melting ice and changes in rainfall that add water to the oceans. GRACE helps distinguish these from changes caused by thermal expansion of the water, which happens as oceans warm. GRACE also reveals changes in deep ocean currents, which transport water and energy around the globe, by measuring changes in the pressure at the bottom of the ocean.

Since NASA launched the GRACE twin satellites in 2002, scientists have had an extremely precise measurement of the contribution that ice sheets' loss of mass contributes to changes in gravity and what it is adding to sea level rise. "Because of GRACE, we've had a pretty good idea of what's happening since 2002," said Steve Nerem of the University of Colorado, head of NASA's Sea Level Change Team. "We know how much [of sea level rise] is from Greenland, how much is from Antarctica, how much is from glaciers."

Seas around the world have risen an average of nearly 3 inches since 1992, with some locations rising more than 9 inches due to natural variation, according to the latest satellite measurements from NASA and its partners. Current research points to an unavoidable sea level rise of several feet in the future.

"GRACE essentially demonstrated a new form of remote sensing for climate research that has turned out even better than we hoped. We realized early on in the design of GRACE that we could measure the gravity field well enough to observe the critical indicators of climate change – sea level rise and polar ice melt," said JPL Director Michael Watkins, former GRACE project scientist.

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