Scientists have discovered the strongest heat wave ever recorded in Antarctica

“It was very clear that it was a remarkable event,” said Edward Blanchard-Wriglesworth, the study’s author. “We found that the temperature anomaly, the temperature anomaly of 39 degrees, is the largest ever measured anywhere in the world.”

March temperatures, which mark a change in autumn on the continent, are typically around minus 54 degrees Celsius on the east coast near Dome C. On March 18, 2022, temperatures peaked at minus 10 degrees Celsius. That’s warmer than even the highest temperature ever recorded during the summer months in that region — “which in itself is pretty incredible,” said Blanchard-Wriglesworth, an atmospheric scientist at the University of Washington.

In the new research, Blanchard-Wriglesworth and his colleagues investigated how and why such an unimaginable heatwave occurs, especially at a time of year when there is less sunlight. They found that extreme heat is largely part of Antarctica’s natural variability, although climate warming has had some effect.

Blanchard-Wigglesworth said the seeds of the heat wave began with unusual winds. Normally, winds blow from west to east around Antarctica and help isolate the continent from warmer regions to the north, allowing it to remain cool. But as happens with heat waves in the United States, the winds meandered and allowed a warm mass of air from southern Australia to move into East Antarctica in just four days — “probably the first time it’s happened at least this quickly,” Blanchard says. – Wigglesworth said.

The northerly winds also brought a lot of moisture, bringing significant amounts of snow, rain and snowmelt to the east coast of the ice sheet.

Meanwhile, Antarctica was experiencing its lowest level of sea ice on record, although the team said their work suggested this did not appear to be affecting the heatwave.

The study found that large fluctuations in weather are not completely out of the ordinary in the polar regions. In an analysis of World Weather Station data and computer simulations, the team found that the largest temperature changes above normal occur at high latitudes. Places like Europe or the lower 48 United States do not experience such anomalous heat waves.

A fundamental reason why the largest anomalies occur at high latitudes is that there is more cold air to be removed closer to the ground, Blanchard-Wriglesworth said. Normally, the air gets colder higher up in the atmosphere. But some places — such as high latitude regions with a lot of snow and ice — have colder air near the ground and warmer air above it, which is called an inversion layer. In these spots, a warm air mass can swoop in to replace cold air and create warm weather. These warm events often occur during or near winter, when inversion layers are strongest.

“This is what we saw with the Antarctic heat wave,” Blanchard-Wriglesworth said. “These events are eroding this coup. You have to get rid of it.”

Meteorologist Jonathan Wylie, who was not involved in the study, said he was not surprised that the Antarctic heatwave recorded the largest temperature anomaly observed anywhere. After all, the Antarctic Plateau has some of the highest temperature variability in the world.

The full role of climate change is still under investigation, although the new study confirms that warmer weather has not played a large role in increasing temperatures. The team ran a set of computer models running scenarios that involved increased greenhouse gas emissions versus a world that did not. They found that climate change only increased the heatwave by 2 degrees Celsius. By the end of this century, climate change may increase this heat wave by an additional 5 to 6 degrees Celsius.

“A 2°C increase for a heatwave that was 39°C above average means this heatwave would have broken records had it not been for the climate change signal,” Wille, the ETH Zurich researcher, wrote in an email.

But climate change could have another effect that the models haven’t tested, such as affecting the anomalous winds that brought warm air mass to the continent in the first place. Wylie said the unusually heavy tropical rains of the previous weeks had created an atmospheric circulation pattern that had never been observed before — leading to the intense heat.

“It is possible that climate change has affected atmospheric dynamics such as tropical convection anomalies that led to the heatwave, but these things are very difficult to pin down,” Wiley said.

More heat waves like this in Antarctica in a warmer world could have dire effects on the ice sheet, Blanchard-Rigglesworth said.

“If you add another five or six degrees on top of that, you start getting closer to the melting point,” Blanchard-Rigglesworth said. If these events become more common in 50 or even 100 years, “this type of event could lead to some impacts that we may not have had on our radar.”