The Washington Post

Greenland temperatur­es rise up to 50 degrees over normal, setting records

- BY IAN LIVINGSTON AND KASHA PATEL Jason Samenow contribute­d to this report.

Temperatur­es soared to record levels in Greenland early this week, up to 50 degrees above normal in some places. Researcher­s say this early warm spell could make its ice sheet more vulnerable to melt events this summer.

Recent summers have brought record-setting melting of the massive ice sheet, which is the world’s largest contributo­r to rising sea levels, outpacing the Antarctic ice sheet and mountain glaciers.

“It was certainly a very unusual event, that such a high temperatur­e was reached in the middle of winter,” Ruth Mottram, a climate scientist at the Danish Meteorolog­ical Institute, wrote in an email. “There was indeed a March record set this week.”

This latest warm spell in Greenland pushed the temperatur­e in its capital, Nuuk, up to 59.4 degrees (15.2 Celsius) on Sunday, the warmest on record for March or April, according to climate expert Maximilian­o Herrera. The average March high in Nuuk, which sits on the southweste­rn coast of the island, is about 23 degrees (minus-5 Celsius).

Computer model analyses showed even more anomalous temperatur­es in the far-northern part of Greenland, between 30 and 50 degrees (17 and 28 Celsius) above normal.

“The data has been checked, and indeed, a new record was set in Nuuk with a temperatur­e of 15.2 degrees Celsius, which never has been observed so early in the course of the year,” confirmed Martin Stendel, a climate researcher at the Danish Meteorolog­ical Institute. He added that temperatur­es in Greenland were warmer than in Copenhagen at the same time.

The warmth is related to a phenomenon that meteorolog­ists call the “Greenland block,” a stagnant zone of high pressure that causes the air to sink and warm beneath it. The block may have developed in response to a sudden warming at high levels of the atmosphere in February. The “sudden stratosphe­ric warming” disrupted the polar vortex, a pool of frigid air that kept Greenland chilly through the core winter months.

But onc e the vortex was jostled in late February, it reshuffled weather patterns, allowing more of the cold air lodged over the Arctic to sink toward the mid-latitudes. The developmen­t of high pressure over Greenland is a frequent response to sudden stratosphe­ric warming events.

“You really see this high-pressure system sitting right there,” said Marco Tedesco, a researcher at the Lamont-doherty Earth Observator­y at Columbia University. “If you think about the way it spins, it’s basically sucking up all the warm air from northeast Canada and then it’s putting it on the ice sheet.”

Tedesco said such high-pressure systems over Greenland occur at some frequency and appeared during melt events in 2012, 2018 and 2019. He said this March event reminded him of the unusually late heat wave in September, which caused extensive melting for the first time on record in that month.

The heat may not induce extensive melting across the ice sheet right now, but researcher­s said it could have repercussi­ons for future heat waves. For instance, it could reduce the amount of fresh snowfall at the beginning of the melt season, which helps cover bare ice.

“Any additional heat even before the melt season can preconditi­on for earlier melts,” said Jason Box, a researcher with the Geological Survey of Denmark and Greenland. “If the temperatur­e of the existing snow is higher than it would otherwise be, there is less heat required to bring it to the melting point.”

Less-protective snow cover could mean that darker bare ice may be exposed quicker, which is problemati­c as it absorbs more sunlight than snow and retains less meltwater. This could have cascading effects for years down the line.

“Even though you might not have a direct contributi­on to the melting and runoff and sea-level rise in this case, you are changing the face of the Greenland ice sheet,” Tedesco said.

With the current Greenland block drifting southwest, the highest temperatur­es compared with normal are shifting out of Greenland and into Nunavut, Quebec, Newfoundla­nd and Labrador in Canada. Record-high temperatur­es are still occurring from northern Greenland into Quebec.

Temperatur­es running up to 35 degrees (20 Celsius) above normal will continue in those areas over the next several days before the warmth dissipates next week. Temperatur­es near and below normal are forecast to return to a large chunk of Greenland as soon as later this week.

The presence of high pressure over Greenland — indicated by what’s known as the negative phase of the North Atlantic Oscillatio­n — has tended to be transient this winter, and that may continue into spring. Such highpressu­re systems have induced melting as early as April in recent years.

Because of human-caused climate change, the Arctic is warming as much as four times as fast as the rest of the globe, and additional rapid warming and melting ice are projected into the future.

Recent research suggests that the Greenland 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 stopped emitting greenhouse gases today.

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