Greenland ice cap melt measured by satellites

Australian scientists have been able to use NASA satellites to accurately weigh how much of Greenland’s ice cap is melting.

The team from Australian National University (ANU) has utilized data from NASA’s current mission, called GRACE-FO, to devise a way of calculating the weight of large masses like the Greenland ice cap.

GRACE-FO stands for Gravity Recovery and Climate Experiment Follow On and it uses a pair of satellites that literally weigh the Earth’s water from space by detecting tiny changes in gravity, caused by changes in mass on Earth.

According to the report of the Australian Broadcasting Corporation (ABC) on Wednesday, in July this year it’s estimated more than 30 billion tonnes of ice melted in three days.

Paul Tregoning, who leads the ANU team in Canberra, said: “One satellite is following 200 kilometres behind the other. The change in distance between the satellites is measured really accurately, down to a 10th of a thickness of a human hair, or about a micro-meter.

“If there is less ice in a location, then there’ll be weaker gravity that will affect the change in distance between the satellites, which is what we measure.”

When a heatwave hit Greenland in early August, Tregoning waited for the NASA data to arrive and went to work on his calculations.

Using the fresh information, Tregoning measured that Greenland this September weighed almost a third of a trillion tonnes less than it did the previous month.

“The mass loss in Greenland between August and September 2019 would amount to 42 millimeters of water covering the whole of Australia, or 4.7 meters over the whole of Tasmania,” Tregoning told the ABC.

The GRACE missions have now been documenting the melting of the Greenland ice cap for 17 years. Ice loss varies from year to year, but the trend is relentlessly downward, said the ABC report.