Earth’s Gravity Dips from Antarctic Ice Loss

 

Oct 1, 2014 01:23 PM ET // by Patrick J. Kiger

Of all the effects on the Earth from human-driven climate change, this one might be the weirdest.

The rapid loss of ice from the West Antarctica’s ice sheet between 2009 and 2012 was big enough to cause a slight dip in the Earth’s gravitational field over the region, according to the European Space Agency. Scientists based the finding upon measurements made by the agency’s GOCE satellite, which from 2009 to 2013 used new technology to map the Earth’s gravitational field in unprecedented detail.

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While we might think of gravity as being the same all over the Earth, it’s actually not quite uniform, because of variations in the Earth’s surface such as mountains, valleys, ocean trenches and, in the case of the polar regions, the ice sheets, according to NASA Earth Observatory. But since a mountain or a valley generally is in the same place from year to year, shifts in gravity in a particular spot usually only take place gradually over very long periods of geologic time.

But in the case of the west Antarctic ice sheet, change is occurring rapidly. Data from another ESA satellite, CryoSat, shows that since 2009, the West Antarctic ice sheet’s rate of shrinkage has increased each year by a factor of three.

While the change in Antarctic gravity is so slight that it wouldn’t be noticeable from the ground, it’s a warning signal.

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The breakup of the West Antarctic ice sheet could have much more serious effects, according to NASA. It the ice disappeared completely, it would raise sea levels by as much as 16 feet. The most vulnerable portion of the sheet is the Amundsen Sea region, where the glaciers don’t have big enough ice shelves to stem ice flow, and mostly aren’t pinned down by obstructions such as islands.

Additionally, a warm current rising up from the sea bottom accentuates the instability of the ice. The breakup of the Amunden Sea ice alone could cause the planet’s oceans to rise by 4 feet.

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