In 2019 Greenland experienced an unusually warm summer, which caused the world’s largest island to lose 600 billion tonnes of ice and raise sea level by 0.2 centimetres, according to a NASA study published on 18 March 2020. This amount of ice loss has more than doubled Greenland’s annual average for 2002-2019.
The data comes from the joint American-German space mission Grace-FO, a pair of satellites orbiting the Earth and recording mass changes corresponding to the Earth’s gravitational field, according to the BBC. The satellites are particularly adept at detecting tiny changes in the Earth’s gravitational field caused by ice gain or loss. According to the Washington Post, they have proven useful in detecting groundwater reservoirs around the globe.
The study also looked at Antarctica and found that it continues to lose ice mass, especially in the Amundsen Sea enclosure and on the Antarctic Peninsula in the western part of the continent, according to NASA’s Jet Propulsion Laboratory.
“We knew that this past summer was particularly warm in Greenland and every corner of the ice sheet has melted,” lead author Isabella Velicogna, senior project scientist at the Jet Propulsion Laboratory and professor at the University of California, Irvine, said in a statement. “But the numbers are really enormous.”
The study was published in the journal Geophysical Research Letters. It tracked Greenland’s ice loss in 2002, based on information from the Grace (Gravity Recovery and Climate Experiment) satellites, which were decommissioned in 2017, and the new Grace-FO satellites, which were launched in 2018. FO stands for Follow On, as reported by the Washington Post.
The satellites revealed that Greenland has lost 4,550 billion tons of ice between 2002 and 2019, an average of 261 billion tons per year, according to the Washington Post. 2012 and 2019 were the two biggest melting years in this time frame, the BBC reported.
Velicogna told the Washington Post that what made 2019 so different in Greenland was that the glaciers in the north and north-east of Greenland were melting rapidly, which was unusual.
“So basically we are melting around the ice sheet,” she said.
In the coastal town of Ilulissat, not far from where the mighty Jakobshavn glacier enters the ocean, temperatures reached temperatures in this summer that reached the high 20s. The warm temperatures even reached the interior of the ice sheet, which was approaching freezing point, the BBC reported.
“It is significant that we are now seeing the melting and mass loss expanding as far as the northern glaciers of Greenland. The whole of Greenland has contributed to last year’s huge summer melt,” Velicogna said according to the BBC.
Robin Bell, an expert on ice sheet dynamics at Columbia University, told the Washington Post that the satellite data will help researchers improve the accuracy of their future estimates of sea-level rise.
“This is a nice update on how we can really see how the ice sheets change … through the annual inhalation and exhalation as snow accumulates in Greenland in winter and melts in summer,” she said.