Greenland nearly melted earlier this month, when over the course of just a few days, 97 percent of the surface area of its entire ice cover defrosted to at least some degree, scientists at NASA have announced.
It was the fastest melt in 30 years of satellite recordkeeping, NASA said in a release. Scientists were astounded when data from three satellites revealed that about 40 percent of the ice sheet’s surface had melted on July 8, growing to 97 percent by the 12th, NASA said.
A melting in itself is not unprecedented, and it’s not necessarily due to climate change, the space agency said. About half of the surface of Greenland’s ice sheet melts every summer, though at higher altitudes it refreezes almost immediately. At the coast, NASA said, some of that melt ends up in the ocean and the rest pools atop the ice.
This particular year, NASA said, “an unusually strong ridge of warm air, or a heat dome,” planted itself above the island country. However, the rapidity and degree caused consternation, since regardless of the cause, a vanishing Greenland ice sheet could boost sea levels even more than they’re already being upped by climate change. Even Greenland’s highest point—Summit Station, two miles above sea level, atop two miles of ice—showed some degree of melt.
That ridge of warm air had dissipated by July 16—but that’s the day a chunk of the Petermann Glacier fell into the Arctic Ocean.
If the entire 656,000-square-mile ice sheet were to melt, it could add 23 feet to the global sea-level rise, the website LiveScience pointed out, quoting a report issued in 2007 by the Intergovernmental Panel on Climate Change (IPCC), the international climate-change-assessment agency.
“Ice cores from Summit show that melting events of this type occur about once every 150 years on average. With the last one happening in 1889, this event is right on time,” said team researcher Lora Koenig, a glaciologist at the NASA’s Goddard Space Flight Center, in the NASA statement. “But if we continue to observe melting events like this in upcoming years, it will be worrisome.”
Thus teasing out the climate-change effects from the naturally occurring melts will only be possible over time, the scientists said. According to LiveScience, global warming due to greenhouse gas emissions is indeed contributing to the melt, with research indicating that the country’s entire ice sheet could disappear in 2,000 years if carbon emissions are not reduced.
“The Greenland ice sheet is a vast area with a varied history of change. This event, combined with other natural but uncommon phenomena, such as the large calving event last week on Petermann Glacier, are part of a complex story,” Tom Wagner, NASA’s cryosphere program manager in Washington, told the Associated Press. “Satellite observations are helping us understand how events like these may relate to one another as well as to the broader climate system.”