Antarctica's ice loss changed Earth's gravity: study

Antarctica has lost so much ice that it has caused a shift in Earth's gravity, according to a new study.
The European Space Agency (ESA)'s GOCE satellite has shown that the ice lost from West Antarctica over the last few years has left its signature.
"The loss of ice from West Antarctica between 2009 and 2012 caused a dip in the gravity field over the region," ESA said in a statement.
More than doubling its planned life in orbit, GOCE spent four years measuring Earth's gravity in unprecedented detail.
Scientists are now armed with the most accurate gravity model ever produced.

This is leading to a much better understanding of many facets of our planet - from the boundary between Earth's crust and upper mantle to the density of the upper atmosphere.

The strength of gravity at Earth's surface varies subtly from place to place owing to factors such as the planet's rotation and the position of mountains and ocean trenches.
Changes in the mass of large ice sheets can also cause small local variations in gravity, ESA said.
High-resolution measurements from GOCE over Antarctica between November 2009 and June 2012 were analysed by scientists from the German Geodetic Research Institute, Delft University of Technology, Netherlands, the Jet Propulsion Lab in US and the Technical University of Munich in Germany.

They found that the decrease in the mass of ice during this period was mirrored in GOCE's measurements, even though the mission was not designed to detect changes over time.
GOCE data could be used to help validate satellite altimetry measurements for an even clearer understanding of ice-sheet and sea-level change, ESA said.
ESA's CryoSat satellite, which carries a radar altimeter, has recently shown that since 2009 the rate at which ice is been lost from the West Antarctic Ice Sheet every year has increased by a factor of three.
Between 2011 and 2014, Antarctica as a whole has been shrinking in volume by 125 cubic kilometres a year, the statement said.