From: Roger Greenway, ENN
Published July 15, 2013 06:02 AM

Satellite monitoring of ice sheets

Data from satellites have been used a lot recently to monitor the loss of ice from ice sheets in Antarctica and Greenland. Having these data is relatively recent, however. It would be better if the data existed for a longer period so more accurate predictions of future rates of ice loss or accretion could be made. 

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The length of the satellite record for the Greenland and Antarctic ice sheets is currently too short to tell if the recently reported speed-up of ice loss will be sustained in the future or if it results from natural processes, according to a new study led by Dr Bert Wouters from the University of Bristol.

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.

The ice sheets covering Antarctica and Greenland contain about 99.5 per cent of the Earth's glacier ice which would raise global sea level by some 63m if it were to melt completely. The ice sheets are the largest potential source of future sea level rise — and they also possess the largest uncertainty over their future behaviour. They present some unique challenges for predicting their future response using numerical modelling and, as a consequence, alternative approaches have been explored. One common approach is to extrapolate observed changes to estimate their contribution to sea level in the future.

Since 2002, the satellites of the Gravity Recovery and Climate Experiment (GRACE) 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.

Dr Bert Wouters, currently a visiting researcher at the University of Colorado, said: "In the course of the mission, it has become apparent that ice sheets are losing substantial amounts of ice — about 300 billion tonnes each year — and that the rate at which these losses occurs 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 observed by satellites. 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 Niño and La Niña events) and slow changes in ocean currents.

Antarctica ice sheet image via Shutterstock.

Read more at Bristol University.

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