Antarctic temperatures soar 50 degrees above norm in long-lasting heat wave

Ground temperatures in East Antarctica have soared more than 50 degrees above normal in the second major heat wave to afflict the region in the past two years. This historic warm spell could persist for another 10 days and is an ominous example of the major temperature spikes this polar climate could experience more frequently in a warming world.

“This heat wave is a near-record (or record) event for the region of Antarctica it’s having the biggest impact on,” Edward Blanchard, an atmospheric scientist at the University of Washington, said in an email. “The heat wave’s large footprint is also remarkable,” as it covers a large section of East Antarctica, which makes up most of the continent.

The heat wave comes in the middle of the Antarctic winter, so temperatures are still hovering around minus-4. Still, the Antarctic temperature anomaly is the largest on the globe, according to weather models.

Temperatures are expected to remain up to 36 to 50 degrees above average in parts of East Antarctica for the next 10 days. They have been substantially above average for most of July, but not as high as they are now. Last week, they climbed to 20 degrees above average.

The South Pole station will clinch its warmest July since 2002, about 11 degrees above average, according to Antarctic temperature analyst Stefano Di Battista. From July 20 to 30, the average temperature at the station was minus-54, which is a typical temperature for the end of February — the end of summer in Antarctica. Vostok, at the center of the eastern ice sheet, will see its warmest July since 2009 at around 12 degrees above average.

“The heat wave on the Antarctic Plateau is extraordinary more for its duration than for its intensity, although some values are notable,” Di Battista said in an email.

While large parts of the continent have been exceptionally warm, a cold snap in the north brought extreme cold earlier in July. On the 17th, weather stations at Dome Fuji plummeted to minus-115.8, its second-coldest July temperature on record.

What is causing the heat wave?

Winter temperatures in Antarctica substantially fluctuate because of the lack of sunlight, but this heat wave is a much larger deviation from the norm than usual. It’s too early to determine all of its causes, but scientists say it may be at least partially linked to processes occurring 20 miles above the surface in the stratosphere.

The stratosphere contains a strong band of cold air and low pressure spinning around each pole, known as the polar vortex. The vortex is typically strong and stable during winter in the southern hemisphere, said Amy Butler, an atmospheric scientist at the National Oceanic and Atmospheric Administration. But this year, she said, it’s been jostled by atmospheric waves, weakening the vortex and causing high-altitude temperatures to soar; this is known as a sudden stratospheric warming event.

“The main reason it is notable is because it is usually a relatively quiet time of year for the Southern Hemisphere polar vortex,” Butler said. This event has lead to some record temperatures high in the stratosphere.

Data shows that the sudden stratospheric warming event is also affecting the lower atmosphere where weather occurs. The warming has weakened the belt of westerly winds around Antarctica, commonly referred to as the jet stream. This has allowed frigid air normally confined near the South Pole to veer north toward New Zealand, southern Africa and southern South America, like a refrigerator door left ajar. As the deep chill has escaped East Antarctica, temperatures have dramatically risen there in response.

Atmospheric pressures over East Antarctica are also surging to “absolutely bonkers” levels, tweeted Ben Noll, a meteorologist based in New Zealand. “The weather in the Southern Hemisphere is a little wild at the moment!” he wrote.

Several other factors may be helping to intensify the heat wave. Antarctic sea ice cover is the second-lowest on record for this time of year — just barely above the record-breaking levels in 2023. Sea ice helps keep the polar regions cool by reflecting sunlight back to space. It also helps keep the air cool by acting as a barrier between the colder air and warm waters below, which have been exceptionally warm this year.

“It is likely that having less sea ice and a warmer Southern Ocean around the Antarctic continent ‘loads the dice’ for warmer winter weather over Antarctica,” Blanchard said. “From this perspective, it might be a bit ‘less surprising’ to see large heat waves in Antarctica this year compared to a ‘normal’ year with average sea ice conditions.”

Scientists say it’s also hard to ignore that the entire world has seen record warmth since last July, consistently exceeding an average of 1.5 Celsius of warming above the preindustrial era. As the globe warms, however, the poles are warming at an even faster rate. Recent ice core data and modeling show Antarctica is warming up twice as fast as the global average.

“With global temperatures increasing, that raises the potential ‘baseline’ for the average temperatures,” said David Mikolajczyk, a research meteorologist at the University of Wisconsin-Madison. As a result, “strong warming events such as this one can occur more frequently and have a bigger impact.”

The largest heat wave in Antarctica — and anywhere in the world — occurred in March 2022, when the eastern coast of Antarctica spiked at least 70 degrees above normal. Scientists on-site wore shorts and removed their shirts, while the area experienced intense melting.

“These heat wave events are, unfortunately, getting less and less surprising to me [in the] last years, when several of these events have occurred,” said Sergi Gonzàlez Herrero, an atmospheric scientist at WSL Institute for Snow and Avalanche Research.

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Jason Samenow contributed to this report.