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GRACE satellites document rapid Greenland ice loss

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There was a pause in melting in 2013, but scientists can’t be sure if this pause is ongoing because of a lack of monitoring infrastructure
by TR Pakistan

Satellites from the Gravity Recovery and Climate Experiment (GRACE) project have documented a four-fold increase in mass being lost from Greenland’s ice sheet from 2003 to 2013. According to scientists, this disturbing revelation means that south-west Greenland — which was previously not considered a threat — could become a major contributor to future sea level rise.

“We knew we had one big problem with increasing rates of ice discharge by some large outlet glaciers, but now we recognise a second serious problem: increasingly, large amounts of ice mass are going to leave as meltwater, as rivers that flow into the sea,” says the study’s lead author Professor Michael Bevis from the Ohio State University.

Scientists who have been concerned about sea level rise have long monitored Greenland’s south-east and north-west regions, where glaciers continually force large chunks of ice into the Atlantic ocean. South-west Greenland however, is devoid of such glaciers.

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“Whatever this was, it couldn’t be explained by glaciers, because there aren’t many there,” said Bevis. “It had to be the surface mass – the ice was melting inland from the coastline.”

Currently, researchers believe this melting occurred as a consequence of a weather phenomenon known as the North Atlantic Oscillations (NAO) which enhances summertime warming and reduces snowfall. However, climate change is also being considered a factor.

“These oscillations have been happening forever… so why only now are they causing this massive melt? It’s because the atmosphere is, at its baseline, warmer. The transient warming driven by the North Atlantic Oscillation was riding on top of more sustained global warming,” said Bevis.

Scientists now believe it is important to increase monitoring of the south-western portion of the Greenland ice sheet. GPS systems in place monitor Greenland’s ice around most of its margin, but the network is sparse in the south-west. Furthermore, the GRACE satellites stopped recording data in 2016. Because of this, it is not clear whether a pause in melting that occurred in 2013 is still ongoing.

Grace (the Gravity Recovery and Climate Experiment) consisted of two Earth-orbiting satellites which took detailed measurements of gravity-field anomalies. This was a joint mission between Nasa and the German Aerospace Center, they were launched in March 2002. Two replacement satellites were launched last year, but have not yet been brought fully online.

Last month, researchers reported that the Greenland melt was unprecedented in 350 years.