(ORDO NEWS) — It’s more like July than September in Greenland right now.
After a fairly cold and wet summer in Greenland, an unusually late heat wave over the weekend caused extensive ice sheet melt – the kind of melt that typically occurs in mid-summer.
The researchers say this is the largest melting event to have occurred in September, based on nearly four decades of data.
“This event demonstrates that global warming is increasing not only the intensity but also the length of the melting season,” said Maurice van Tiggelen, a polar scientist at the University of Utrecht in the Netherlands, in an email.
The first day of September usually marks the end of the Greenland melt season, as the sun dips lower into the sky and temperatures tend to drop.
However, temperatures began to rise over the weekend as warm air moved north through Baffin Bay and the west coast of Greenland.
As a result, tens of billions of tons of ice have been lost, an event that could further increase Greenland’s already significant contribution to sea level rise.
As the climate changes, researchers expect that longer and stronger periods of warming will affect the ice sheet, increasing overall melting.
In the period from Friday to Monday, several weather stations recorded the maximum air temperature for the entire year.
In western Greenland, temperatures rose 36 degrees Fahrenheit (20 degrees Celsius) above normal for this time of year.
At the top, traditionally the coldest part of the ice sheet, temperatures even rose above the melting point on Saturday, according to NOAA observations at the National Science Foundation’s Summit Station.
“It’s really amazing to see such a heat wave hitting Greenland in September,” Ted Scambos, a senior research fellow at the University of Colorado, said in an email.
“For the first time in history, temperatures at the summit exceeded the melting point in September, on the afternoon of September 3rd.”
The heat caused about 35 percent of the ice sheet to melt over the weekend – the kind of large-scale melt that typically occurs in July. Typically, only 10 percent of the ice sheet’s surface melts in early September.
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The melting conditions also created a hurdle for researchers in the area: Van Tiggelen and colleagues were working in the southern part of the ice sheet, but were forced to shorten their stay to avoid heavy rainfall. He also said the ice surface was more slippery than when visiting on sunny days in previous years.
According to climatologist Xavier Fettweis, during the peak of the melt on Saturday, the rate of melt water flow reached 12 billion tons per day, which can easily be attributed to the 10 largest flows on record.
Fettweiss explained that meltwater runoff is important to monitor because it can enter the ocean and contribute to sea level rise.
Part of the runoff can also linger in the snow cover and freeze in winter. However, such an unusually late melt could contribute to the formation of ice slabs on top of the snowpack, he said.
Ice slabs can prevent meltwater from seeping through the snowpack, which means it can enter the ocean, contributing to further sea level rise.
“If such events occur in the coming summers (which is very likely), the contribution to sea level rise will [increase],” Fettweis wrote in an email.
Overall, Scambos estimates that Greenland lost about 20 billion tons of ice during the weekend event. This is about 7 percent of the total ice that falls in a typical year. For every 360 billion tons of ice lost, sea levels rise by one millimeter.
Greenland is already the largest contributor to sea level rise, ahead of the Antarctic Ice Sheet and mountain glaciers.
Over the past two decades, the rate of ice sheet melt has increased as the Arctic warms faster than the rest of the world.
New research suggests that the ice sheet will lose about 3 percent of its current mass – a volume equal to just under a foot of sea level rise – even if the world stops emitting greenhouse gases today.
“Greenland’s icy rim cannot bear the conditions that are becoming more familiar to it. This event is typical of such destabilizing conditions,” Scambos said.
With the exception of the last event, this year’s ice melt season in Greenland has been fairly mild. Prior to this heat wave, the most notable phenomenon was a “thermal ripple” that caused a moderate melt in mid-July, and after this event, the number of melt days was almost average.
Researchers are concerned about the long-term consequences of such extreme one-time events. Over time, warmer temperatures and more frequent extreme events will cause Greenland to melt more completely, accelerating its mass loss.
This is the second year in a row that an unusually late heat wave has swept over the ice sheet. On August 14, 2021, temperatures rose 18 degrees Celsius above average and caused rain for the first time in history on the top of the ice sheet, located about two miles above sea level. At the time, researchers said it was the largest melting event to occur so late in the year.
Fettweiss said both the August 2021 event and the current event have been linked to more rainfall and the intrusion of wet clouds – an increasingly common source of Greenland’s melt. He said such weather systems “are new in the history of the ice sheet.”
Meanwhile, abnormally warm temperatures and cloudiness persisted over Greenland on Tuesday. Temperatures at the summit have been a little warmer than 28.4 degrees Fahrenheit (minus 2 degrees Celsius) lately, while average temperatures elsewhere in the high Arctic are rapidly dropping below freezing.
“The same major weather shower has been happening for the fourth day in a row,” said Christopher Shuman, a researcher at the University of Maryland Baltimore County and NASA.
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