Loss of ice in Antarctica has been discussed extensively due to its implications for rising sea levels and the changing landscape of the continent, but it turns out that there is another unexpected effect: dips in gravity.

The ESA's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) satellite obtained high-resolution measurements of Antarctica's gravitational field between November 2009 and June 2012. Recent analysis led by Johannes Bouman of the German Geodetic Research Institute found that where the ice has been receding, so has the gravity field. The paper has been published in the journal Geophysical Research Letters. 

In order to monitor the melting, draining, and regrowth of Antarctica's ice more precisely, it has been divided up into catchment basins. GOCE is the first instrument sensitive enough to detect local changes in gravity specific to each individual basin. Additionally, GOCE's data provides geologists with insights into earthquakes and volcanic activity.

GOCE's measurements were combined with data from NASA's Gravity Recovery and Climate Experiment (GRACE), an older satellite whose readings are more coarse. Together, they were able to generate an extremely accurate and detailed model of Earth's gravity field, even exploring the differences between the upper mantle and crust of the planet, as well as determining the upper atmosphere's density.

This is the 2011 GOCE geoid that represents variations in height. Copyright ESA/HPF/DLR

This gravity model can be incorporated with data collected from ESA's CryoSat satellite, which is a radar altimeter used to record depth of Arctic and Antarctic ice, as well as variations in sea levels. This will allow scientists to have a better understanding of this ever-changing landscape. 

Due to the effects of climate change, Antarctica is losing ice mass at an unprecedented rate. Every year since 2009, the rate of ice melt has increased by a factor of three from the previous year. There has been a loss in ice volume of about 125 cubic kilometers (78 cubic miles) of ice each year for the last three years. This loss was well reflected within the GOCE/GRACE gravity model and could be used to predict losses in the future as well. 

“We are now working in an interdisciplinary team to extend the analysis of GOCE’s data to all of Antarctica," Bouman said in a press release. “This will help us gain further comparison with results from CryoSat for an even more reliable picture of actual changes in ice mass.”