Status: 26/09/2023, 13:10 p.m.
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Ice floes in the sun in the polar region of Antarctica (symbolic image). © Sergio Pitamitz/robertharding/Imago
In Antarctica, of all places, it was 2022 degrees too hot in March 39. Researchers are investigating how and why this could have happened.
Antarctica – In March 2022, temperatures near the east coast of Antarctica rose 39 degrees Celsius (70 degrees Fahrenheit) above normal – according to a recent study, this was the most intense heatwave ever recorded on Earth. At that time, the researchers in the field wore shorts and some even took off their shirts to bask in the (relative) warmth. Scientists in other places said that such a high was unthinkable in this region of the world.
"It was just obvious that it was a remarkable event," said Edward Blanchard-Wrigglesworth, author of the study. "We found this temperature anomaly, the 39-degree temperature anomaly, which is the largest ever measured anywhere in the world."
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Temperatures in March, which marks the transition to autumn on the continent, are usually 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 recorded in the region during the summer months — "that's pretty incredible in itself," said Blanchard-Wrigglesworth, an atmospheric scientist at the University of Washington.
How could such an unimaginable heat wave occur in Antarctica?
In the new study, Blanchard-Wrigglesworth and his colleagues looked at how and why such an unimaginable heat wave could occur, especially at a time of year when there is less sunlight. They found that the extreme heat is largely attributable to Antarctica's natural variability, even though global warming had some impact.
The reason for the heat wave, according to Blanchard-Wrigglesworth, was unusual winds. Normally, the winds around Antarctica blow from west to east, helping to isolate the continent from the warmer regions farther north, keeping it cold. But, as with heatwaves in the United States, the winds meandered, allowing a warm air mass from South Australia to reach East Antarctica in just four days — "probably the first time it has happened at least this quickly," Blanchard-Wrigglesworth said.
The northerly winds also brought a lot of moisture, causing significant snow, rain, and melt on the east coast of the ice sheet.
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At the same time, Antarctica recorded the lowest level of sea ice since records began, but this does not seem to have any effect on the heatwave, according to the team.
The greatest temperature fluctuations occur at high latitudes
According to the study, large weather fluctuations in the polar regions are not entirely uncommon. In an analysis of data from global weather stations and computer simulations, the team found that the largest temperature fluctuations occur at high latitudes. In places like Europe or the Lower 48 of the United States, such anomalous heat waves never occur.
According to Blanchard-Wrigglesworth, there is a simple reason that the greatest anomalies occur at these high latitudes: there is more cold air to remove near the ground. Normally, the air gets colder higher in the atmosphere. But in some places — such as high latitudes with lots of snow and ice — the air near the ground is colder and the air above it is warmer, which is called the inversion layer. In these places, a warm air mass can enter, displacing the cold air and creating warm weather. These warm events often occur during or around winter, when the inversion layers are at their strongest.
"That's exactly what we saw with the Antarctic heatwave," Blanchard-Wrigglesworth said. "Through these events, the inversion is hollowed out, so to speak, you get rid of it."
Meteorologist Jonathan Wille, who was not involved in the study, said he was not surprised that this Antarctic heatwave was recorded as the largest observed temperature anomaly ever. After all, the Antarctic Plateau is one of the areas with the greatest temperature fluctuations in the world.
The full role of climate change is still being investigated, although the new study claims that the warmer atmosphere hasn't played a major role in raising temperatures. The team ran a series of computer models with scenarios that included an increase in greenhouse gas emissions compared to a world where this was not the case. They found that climate change caused the heat wave to rise by only 2 degrees Celsius. By the end of the century, climate change could intensify such a heat wave by another 5 to 6 degrees Celsius.
"An increase of 2 degrees Celsius in a heatwave that was 39 degrees above average means that even without the signal of climate change, this heatwave would have been record-breaking," Wille, a researcher at ETH Zurich, wrote in an email.
Climate change may have had an impact
But climate change may have had another effect that the models didn't test, such as the effects on the anomalous winds that brought the warm air masses to the continent in the first place. Wille said that unusual tropical rainfall in the weeks before created an atmospheric circulation pattern that had never been observed before and led to the extreme heat.
"It's possible that climate change affected atmospheric dynamics, such as the tropical convection anomalies that led to the heatwave, but it's very difficult to quantify those things," Wille said.
Blanchard-Wrigglesworth said more heatwaves like this one in Antarctica could have dire effects on the ice sheet in a warmer world.
"If you add another five or six degrees, you're getting closer to the melting point," Blanchard-Wrigglesworth said. If these events occur more frequently in 50 or even 100 years, "these types of events could have effects that we might not have had on our radar."
About the author
Kasha Patel writes the weekly Hidden Planet column, which covers scientific topics related to Earth, from our inner core to space storms aimed at our planet. It also reports on weather, climate and environmental issues.
We are currently testing machine translations. This article has been automatically translated from English into German.
This article was first published in English by "Washingtonpost.com" on September 24, 2023 - in the course of a cooperation, it is now also available in translation to the readers of IPPEN. MEDIA portals.
