Though not designed to detect changes in the Earth’s gravity over time, the European Space Agency’s GOCE satellite’s high-resolution measurements combined with NASA-German GRACE data has done just that.
The GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite has been measuring Earth’s gravity in great detail for the past four years – more than double its original planned life in orbit.
In doing so, it has produced the most accurate gravity model of the Earth, providing scientists with greater understanding of things like the boundary between Earth’s crust and upper mantle and the density of the upper atmostphere.
Earth’s force of gravity varies subtly from place to place, affected by the planet’s rotation or the position of mountains and ocean trenches. As such, changes in the mass of large ice sheets can also have a local effect.
Scientists from the German Geodetic Research Institute, Delft University of Technology in the Netherlands, the Jet Propulsion Lab in the US and the Technical University of Munich in Germany have been analysing GOCE’s measurements from West Antarctica over the period between November 2009 and June 2012.
They compared these figures to data from GRACE, the Gravity Recovery and Climate Experiment, which is on a mission to accurately map variations in the Earth’s gravity field over time using two satellites, GPS receivers and a microwave ranging system.
GRACE is a joint partnership between NASA and the German Aerospace Centre and its studies include exchanges between ice sheets or glaciers and the oceans.
However, GRACE’s measurements are less refined than GOCE’s, which has the ability to analyse Antarctica’s smaller ‘catchment basins’, divisions within the ice sheet made for the sake of comparison.
These scientists realised that the decrease in the mass of ice during this period was mirrored in GOCE’s measurements, illustrating the effects of ice lost from West Antarctica through dips in the gravity field.
By combining GOCE’s high-resolution measurements with information from GRACE, scientists can now look at changes in ice mass in small glacial systems – offering even greater insight into the dynamics of Antarctica’s different basins.
Melting glacier image by Bernhard Staehli via Shutterstock