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article imageAntarctic ice melts causing shift in Earth's gravity

By Karla Lant     Oct 2, 2014 in Science
The effects of climate change are now so profound that gravity itself is changing. The European Space Agency (ESA) announced Friday that Antarctica has lost enough ice in only three years to cause a shift in the Earth's gravitational pull.
The effects of climate change are now so profound that gravity itself is changing. The European Space Agency (ESA) announced Friday that Antarctica has lost enough ice in only three years to cause a shift in the Earth's gravitational pull.
“The loss of ice from West Antarctica between 2009 and 2012 caused a dip in the gravity field over the region,” writes the ESA. “And, between 2011 and 2014, Antarctica as a whole has been shrinking in volume by 125 cubic kilometers a year.”
The ESA's Gravity field and steady-state Ocean Circulation Explorer Satellite (GOCE), launched in 2009, measured these changes. You can see a video that visualizes them here.
While in some senses this doesn't seem like a major impact, it is highly significant as part of the overall havoc being wreaked by climate change. Earlier this year a completely different team of researchers from NASA and the University of California, Irvine (UC Irvine) announced that multiple major glaciers in West Antarctica have begun an “unstoppable collapse” and have “passed the point of no return”:
“This sector will be a major contributor to sea level rise in the decades and centuries to come,” writes glaciologist and lead author Eric Rignot of UC Irvine and NASA's Jet Propulsion Laboratory (JPL). “A conservative estimate is it could take several centuries for all of the ice to flow into the sea.”
So these are events that are too far gone to stop, and the best case scenario is that as a result global sea levels will rise by several meters over the next few hundred years — not a long time.
And what about the gravity issue? Most of us learned about Newtonian physics in basic high school courses. These courses told us that gravity is a constant, but this isn't completely accurate; it actually varies slightly based on your location on the planet and the density of whatever is underneath you, rock, groundwater, ocean currents, or ice. Other factors impact gravity too, and ESA launched GOCE to measure variations in gravity and observe what causes them.
In the time GOCE has been operating ESA has reported that gravity changes over time. For example, gravity “scars” left by earthquakes such as the 2011 Japanese earthquake vary slightly over time. This is how ESA got the results about Antarctica's melting ice and gravity dipping.
The GOCE satellite takes high-resolution measurements of the gravitational field and scientists combine those with results from Grace, another satellite mission. Grace, operated by the U.S. and Germany, provides lower resolution gravity analysis. The combined results allow ESA experts to see the clearest gravitational changes, and other satellites provide melt maps. CryoSat, for example, shows an increase in ice loss from West Antarctica of at least three times since only 2009. Greenland and Antarctica together now lose approximately 500 cubic kilometers of ice annually; that’s a Manhattan-sized iceberg three-and-a-half miles thick.
More about West Antarctic Ice Sheet, West antarctic ice, antarctic ice melting, Climate change, climate change science
 
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