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.