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.
“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. Researchers at the Danish Meteorological Institute confirmed the record, stating the temperature surpassed the previous March record of 55.7 degrees (13.2 Celsius) in 2016 and previous April record of 58.2 degrees (14.6 Celsius) in 2019.
Martin Stendel, a climate researcher at the Danish Meteorological Institute, said Sunday’s measurement was the warmest on record so early in the year and warmer than Copenhagen at the same time. 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 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 once 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 high-pressure 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.
Jason Samenow contributed to this report.