The same heat dome that roasted Europe and broke national temperature records in five countries last week has shifted to Greenland, where it is causing one of the biggest melt events ever observed on the fragile ice sheet.
The fate of Greenland’s ice sheet is of critical importance to every coastal resident in the world, since Greenland is already the biggest contributor to modern-day sea level rise. The pace and extent of Greenland ice melt will help determine how high sea levels climb and how quickly.
As a result of both surface melting and a lack of snow on the ice sheet this summer, “this is the year Greenland is contributing most to sea level rise,” said Marco Tedesco, a climate scientist at Columbia University.
To illustrate the magnitude of ice contained in Greenland, consider that if the entire ice sheet were to melt, it would raise sea levels by 23 feet. Scientists are using aircraft, field research, satellites and other tools to improve their understanding of how quickly ice is being lost.
Jason Box, a climate scientist who studies Greenland’s ice sheet, examined recent field data from two locations on the ice sheet, both of which showed more ice loss so far during this event than in 2012.
- At one location, 75 miles east of Nuuk, Greenland’s capital, the equivalent of 8.33 feet of water (2.54 meters) had melted as of July 31, slightly exceeding the value of 8.27 feet (2.52 meters) from 2012.
- At another location 497 miles to the north, the equivalent of 7.38 feet (2.25 meters) of water had melted, topping the record of 6.30 feet (1.92 meters) in 2012. In an email, Box said the 2019 melt at this location is twice the average over the last decade.
The Danish Meteorological Institute tweeted that more than half the ice sheet experienced some degree of melting on Tuesday, according to a computer model simulation, which made it the “highest this year by some distance.”
According @dmidk's high res weather model #HARMONIEAROME we calculate a melt area of more than 51% yesterday (>1mm water equiv) - highest this year by some distance#Greenland #icesheet also lost >7 Gigatonnes of ice net of fresh snow/rain in SE https://t.co/Ftg0fkkwJc pic.twitter.com/GZbGTIYB3Z
— Greenland (@greenlandicesmb) July 31, 2019
But the peak of this melt event is likely still to come Wednesday or Thursday.
Xavier Fettweis, a climate scientist at University of Liège, tweeted that a computer simulation suggests the rate of melting will reach a maximum Thursday, which “could be the highest in Greenland history from 1950.”
Already this year, the ice sheet has endured exceptional melting. Between June 11 and 20, the ice sheet lost the equivalent of 80 billion tons of ice, the National Snow and Ice Data Center computed. Melting covered about 270,000 square miles, the most on record so early in the season. Temperatures leaped nearly 40 degrees above normal at the time.
The current record-setting heat dome parked over the ice sheet is bringing nearly cloudless skies and temperatures up to 30 degrees above average.
Even the National Oceanic and Atmospheric Administration’s weather observatory located at the National Science Foundation’s Summit Station, the ice sheet’s highest elevation (10,551 feet), has exceeded the freezing point.
Christopher Shuman, a glaciologist at the University of Maryland-Baltimore County and NASA Goddard Space Flight Center, said the temperature at Summit Station topped 32 degrees for at least eight hours Tuesday, exceeding the warmth during the 2012 melt event “in both magnitude and duration,” even surpassing 33.8 degrees (1 Celsius). The temperature may pass freezing yet again Wednesday and “we’ll get two straight days of substantial melt,” he said.
Tedesco said the overall surface melting on the ice sheet this summer still trails that of 2012, which saw considerable ice loss continue through August. However, he said, the ice sheet’s surface mass balance, which takes into account not only melting but also snow accumulation, is “neck and neck” with that of 2012.
Given the ongoing melt event, “there is very good chance we will have a record-breaking [low] surface mass balance,” Tedesco said. The depleted surface mass on the ice sheet is directly tied to its contribution to sea level rise.
Historical context
The warmth right now constitutes a spike amid a longer period of above average temperatures across Greenland, John Cappelen of the Danish Meteorological Institute said. “July has been warm for the world’s largest island, as the months before. Since April temperatures most places have been high with records broken,” Cappelen said via email.
Ruth Mottram, a climate scientist with the DMI, said the ongoing melt event appears to be “very significant.”
Regarding the longer-term context, Mottram said that preliminary data shows that “every single DMI weather station in Greenland has had a significantly warmer than average July, by 2-3°C depending on where you look — on top of the warmer than average April, May and June.”
Looking back even further, a study published late last year found that surface melting on Greenland is unprecedented in at least the past 350 years.
Twila Moon, a research scientist at the National Snow and Ice Data Center, says the bigger picture of Arctic warming, permafrost melt, spring snow melt, ice loss and other trends are the major concern, as compared with short-lived melt events.
“Any individual melt event is not the thing that is putting Greenland over a tipping point,” Moon said.
The Arctic overall is warming at more than twice the rate of the rest of the globe, which is a trend that has been firmly tied to human emissions of greenhouse gases. “It’s a direct consequence of human-caused climate change,” Moon said.
There’s still time to take action and limit Greenland ice loss, she emphasized, saying that decisions we make now about greenhouse gas emissions will “have an influence on how much and how quickly we lose ice in Greenland and all around the world.”