In the middle of the austral winter, Antarctica suffers a worrisome ‘heat wave’ – Technologist

An average of 10°C above normal in July: Antarctica has been experiencing a significant heat wave for several weeks now, while the Southern Hemisphere is in the midst of the winter season. The icy continent is currently the most unseasonably warm on the planet, with ground temperatures in the east of the continent 28°C above normal on some days. A September 2023 study claimed that Antarctica was the fastest-warming place in the world, warming on average twice as fast as the rest of the planet.

In this winter period, the interior of the icy continent, at an altitude of over 3,000 meters, normally records temperatures of between −50°C and −60°C. But on Monday, August 5, it was −40°C in East Antarctica, according to data from Climate Reanalyzer. On Tuesday, Russia’s Vostok base recorded a temperature of −34°C.

This is not the first time such a “heat wave” has affected Antarctica: In March 2022, the continent experienced an unprecedented anomaly. “It’s not uncommon to have 10°C deviations. What’s different here is that it’s been like this for more than 10 days,” emphasized Gaétan Heymes, an engineer at Météo-France. But, “unlike March 2022, we’re not going to reach near-zero or positive temperatures.”

As Jamin Greenbaum, a geophysicist at the Scripps Institution of Oceanography at the University of California, San Diego, pointed out, Antarctic temperature records are particularly recent, and don’t go back as far in time as other continents. “The current situation is undoubtedly very alarming. An event like this is extremely unusual on the records we have in Antarctica,” he stated. For Jonathan Wille, climate scientist at ETH Zurich (Switzerland), “what is also remarkable is the surface area covered by this heat wave, comparable to the whole of Australia.”

Weakening of the polar vortex

Scientists are not unanimous as to the precise and immediate cause of these temperatures, which are far too high for the season and the region. “Atmospheric science is very complex, and the scarcity of data and history we have, particularly over Antarctica, complicates matters even further,” said Heymes. Some researchers have suggested a weakening of the polar vortex. Winds formed by air masses rotate naturally around the Earth’s two poles, in the stratosphere. When they weaken, temperatures rise, especially at high altitudes like in East Antarctica.

According to Emmanuel Le Meur, a glaciologist at the Institut des Géosciences de l’Environnement (IGE) in Grenoble (southeastern France), “when the polar vortex is disrupted, a phenomenon known as atmospheric rivers can occur.” These are corridors of moisture in the atmosphere, created by the meeting of two different air masses, which can cause widespread precipitation. This weakening of the polar vortex is, according to some scientists, a consequence of climate disruption. “Research shows that extreme temperatures are becoming increasingly common on this continent,” added Wille. Until very recently, “an event of this magnitude was thought to have a return period of 100 years,” explained Le Meur, “but two years on, it’s happened again. In lesser proportions, but still.”

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