The satellite that detected the melting is Gravity Recovery and Climate Experiment (GRACE). British scientists have been using it since 2002 to detect tiny variations in Earth's gravity field resulting from changes in mass distribution, including movement of ice into the oceans.
Using these changes in gravity, the state of the ice sheets can be monitored at monthly intervals.
Scientists from University of Bristol also found that the rate at which ice sheets are losing ice is increasing. Compared to the first few years of the GRACE mission, the ice sheets' contribution to sea level rise has almost doubled in recent years. Yet, there is no consensus among scientists about the cause of this recent increase in ice sheet mass loss.
Beside anthropogenic warming, ice sheets are affected by many natural processes, such as multi-year fluctuations in the atmosphere (for example, shifting pressure systems in the North Atlantic or El Nino and La Nina events) and slow changes in ocean currents. The ice sheets covering Antarctica and Greenland contain about 99.5% of the Earth's glacier ice which would raise global sea level by some 63 metres if it were to melt completely. The ice sheets are the largest potential source of future sea level rise.
The findings, published in Nature Geoscience, underscore the need for continuous satellite monitoring of the ice sheets to better identify and predict melting and the corresponding sea-level rise.
Lead researcher Dr Bert Wouters and his team compared nine years of satellite data from the GRACE mission with reconstructions of about 50 years of mass changes to the ice sheets. They found that the ability to accurately detect an accelerating trend in mass loss depends on the length of the record.
At the moment, the ice loss detected by the GRACE satellites is larger than what we would expect to see just from natural fluctuations, but the speed-up of ice loss over the last years is not.
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