For the first time ever, Greenland experienced widespread melting in September


In Greenland, it’s more like July than September.

After a somewhat cold and humid Greenland summer, an unusually late heat wave last weekend caused widespread thaw across the ice sheet – a kind of melt Usually seen in the middle of summer. Researchers say it’s the largest melting event that occurs in September, according to nearly extended data sets Four decades.

“This event shows how global warming is not only increasing the intensity but also lengthening the melt season,” polar scientist Maurice van Tejlen from Utrecht University in the Netherlands said in an email.

The first day of September marks the end of Greenland’s thaw season, as the sun moves lower in the sky and temperatures are usually cool. However, temperatures began to rise over the weekend when a warm jet of air blew north across Baffin Bay and the west coast of Greenland. As a result, tens of billions of tons of ice were lost – an event that could boost Greenland’s already large contributions to rising sea levels.

As the climate changes, researchers expect longer and stronger periods of warmth to affect the ice sheet – leading to an increase in overall melt.

Between Friday and Monday, several weather stations recorded their own Max air temperature All year round. Parts of western Greenland have risen to 36 degrees Fahrenheit (20 degrees Celsius) above normal for this time of year. The summit, which is traditionally the coldest part of the ice sheet, rose above its melting point on Saturday according to NOAA observations at the National Science Foundation. summit station.

“It’s really amazing to see a heat wave like this covering Greenland in September,” Ted Schampos, a senior researcher at the University of Colorado, said in an email. “For the first time ever, temperatures at the summit exceeded the melting point in September, on the afternoon of September 3rd.”

The heat drove melt across about 35 percent of the ice sheet last weekend – widespread melting of the kind usually observed in July. Usually only 10 percent of the ice sheet’s surface melts in early September.

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The thawing conditions also created obstacles for researchers in the area: Van Tiggelen and colleagues were working on the southern part of the ice sheet but had to shorten their stay to avoid a major precipitation event. He also said that the surface of the ice was more slippery than it had been during visits on sunny days in previous years.

At the height of the melt on Saturday, meltwater runoff rates were recorded as high as 12 billion tons per day — making it one of the 10 largest runoff events on record, according to climate scientist Xavier Fettweis.

Fatwis explained that meltwater run-off is important to keep track of Because it can reach the ocean and contribute to sea level rise. Part of the runoff can also be retained in the snow mass and re-frozen during the winter. However, he said, this unusually late melting may help form ice sheets at the top of the snow mass. Ice sheets can prevent melt water from seeping through the ice mass, which means it can enter the ocean instead, further contributing to sea level rise.

“If such events occur next summer (which is very likely), the contribution at sea level will occur [grow] Akbar,” Fatwa wrote in an email.

In total, Greenland is estimated to have lost about 20 billion tons of ice during the weekend event, according to Scampus. This is about 7 percent of the total ice shed in a typical year. For 360 billion tons of ice lost, sea level rises by one millimeter.

Greenland is already the largest contributor to rising sea levels, surpassing the Antarctic ice sheet and mountain glaciers. Melting rates above the ice sheet have increased in the past two decades as the Arctic is warming faster than the rest of the world. new search He suggests that the ice sheet would lose about 3 percent of its current mass – a volume equal to just under sea level rise – even if the world stopped emitting greenhouse gases today.

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“Greenland’s icy edge cannot withstand the conditions that are becoming increasingly common for it. This event is typical of those destabilizing conditions,” said Schampos.

Outside of the latter event, this year’s thaw season in Greenland has been fairly mild. Prior to this heat wave, the most notable measure was “heat ripple“Which caused an average melt in mid-July, and the number of melt days was close to average after the event.

Researchers are concerned about the long-term consequences of such extreme one-time events. Over time, a warmer temperature regime and more frequent extremes will lead to more mass melting of Greenland, accelerating its mass loss.

This is the second year in a row that an unusually late heat wave has swept the ice sheet. On August 14, 2021, temperatures rose 18°C ​​above average and caused rain to fall on top of the ice sheet, about two miles above sea level, for the first time ever. in time, The researchers said The biggest melting event was late in the year.

How moist air, intensified by climate change, is melting Greenland’s ice

Fatwis said that both the August 2021 event and the current event are associated with large amounts of rain and wet clouds invading the area, increasingly popular source for thaw events in Greenland. These weather systems, he said, are “new to the ice sheet’s history.”

Meanwhile, abnormally warm temperatures and cloudy conditions continued over Greenland on Tuesday. Temperatures have recently been a little warmer than minus 28.4 degrees Fahrenheit (minus -2 degrees Celsius) at the summit, while average temperatures elsewhere in the High Arctic are rapidly dropping below freezing.

“The same basic flow of weather is happening for the amazing fourth day in a row,” said Christopher Schumann, a research scientist at the University of Maryland Baltimore County and NASA.

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