Greenland temperatures surge up to 28C above normal, setting records
Temperatures soared to record levels in Greenland early this week, up to 28C 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.
This latest warm spell in Greenland pushed the temperature in its capital, Nuuk, up to 15.2C 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 -5C.
Computer model analyses showed even more anomalous temperatures in the far-northern part of Greenland, between 17 and 28C 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 Tedesco said it could make it more vulnerable to for future heat waves. For instance, it could reduce the amount of fresh, white snowfall at the beginning of the melt season, which helps cover bare ice on the surface.
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https://www.stuff.co.nz/environment/climate-news/300825068/greenland-temperatures-surge-up-to-28c-above-normal-setting-records