Record heat wave in Antarctica brought exceptional snow, rain and melting

Antarctica has entered fall, yet temperatures rose 70 degrees (39 Celsius) above normal last week on its eastern ice sheet — an unprecedented occurrence for any time of year. Scientists on-site even appeared to strip down to shorts and no T-shirt to celebrate the occasion.

Satellite imagery and computer models indicate significant snow, rain and melting also occurred. During the heat wave, the ice sheet experienced its fourth-wettest day in more than four decades, according to the Modèle Atmosphérique Régionale (MAR), a regional climate model that studies the melting of the polar ice caps.

“Usually, the climate of Antarctica is too cold to have significant accumulation of snow and most of liquid water from melt or rainfall is absorbed by the snowpack and refreezes,” Xavier Fettweis, a climate scientist from the University of Liège who coordinates the development of MAR, wrote in an email. Yet, Fettweis said snowfall led to the ice sheet gaining 69 gigatons of mass from March 16 to 18, three times the usual rate.

The MAR indicates the heaviest precipitation occurred near the coast, with rainfall accumulation of more than an inch, or 50 millimeters. (Note that these values are not direct measurements but modeled quantities based on atmospheric conditions.)

“That would be tremendous for that area,” said Jonathan Wille, a researcher studying polar meteorology at Grenoble Alpes University in France. “It doesn’t even rain here almost ever. Normally they have like a few millimeters of rain per year. And it’s March — it should be getting cold.”

The model also showed some melting along the coastline, although it appears to be very localized. While some areas, like the Totten Glacier, appear to have experienced some melt, other glaciers along the coastline appeared largely unaffected. In any case, this one melt event will not affect the stability of the glaciers in the area presently, Wille said.

The precipitation occurred when circulation patterns around Antarctica directed a very strong atmospheric river, or strip of moist air, into the eastern coastline of the continent on March 15. Atmospheric rivers typically drop about 10 to 20 percent of all snowfall across East Antarctica.

“Moisture intrusion events and atmospheric rivers — they do happen, but this is just to a different degree of intensity,” Wille said. He said the duration and intensity of the event were greater than scientists would normally expect.

The warm, moist air mass was then squished on the Antarctic interior for days as a strong blocking high-pressure system, or “heat dome,” moved into the region — causing temperatures to soar like never before.

The Russian meteorological observatory Vostok — about 808 miles from the South Pole and 11,444 feet above sea level — hit 0.1 degrees (minus-17.7 Celsius) on March 18. The record high shattered the monthly record of minus-26.7 (minus-32.6 Celsius) set on March 4, 1967. The average high temperature at the station is around minus-63 (minus-53 Celsius) in March.

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The Concordia Research Station, about 350 miles from Vostok, hit its highest temperature on record for any month at 10 degrees (minus-12.2 Celsius). Typical high temperatures in March hover around minus-56 (minus-48.7 Celsius). The previous all-time high temperature was 7.34 degrees (minus-13.7 Celsius) on Dec. 17, 2016.

Temperatures on the eastern ice sheet remained above average through Monday and began to slowly return to normal. On Tuesday, Vostok recorded minus-50 degrees (minus-45.7 Celsius).

Temperatures in western Antarctica and near the South Pole remained cold last week. On March 18, the Amundsen-Scott South Pole Station recorded minus-60 degrees (-51.4 degrees Celsius), which is typical for this time of year.

While more research is needed to study the climate change connection, researchers are comparing the event to the Pacific Northwest heat wave in June 2021, which broke temperature records by 10 degrees or more in spots.

Pacific Northwest heat wave was ‘virtually impossible’ without climate change, scientists find

That heat wave event “was something that wasn’t thought to be possible until it actually happened. It was never observed before, and the atmosphere patterns that led to it happening were just not thought to be possible either until it happens,” Wille said. “And that’s what’s basically happened here over Antarctica.”

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