It may be winter in the Southern Hemisphere, but Antarctica is experiencing a long-lasting heat wave

The middle of winter has brought a heat wave to Antarctica, and could last for a few more days. This is the second major heat wave for Antarctica in the last two years.

Antarctic heat wave
The heat wave in Antarctica has some regions seeing temperatures over 50 degrees above average.

Temperatures right now in Antarctica are nearly 50 degrees (28 Celsius) above average. The heat wave is expected to last another 10 days and is a look into what’s to come in a continually warming world.

No matter the season

The heat wave in Antarctica right now is a near-record event for this region, according to Edward Blanchard, an atmospheric scientist at the University of Washington. This heat wave is spanning a large section of East Antarctica, and making up most of the continent. Though it is the middle of winter in the Antarctic, temperatures at -4 degrees (-20 Celsius) are above average.

Temperatures are expected to stay 36 to 50 degrees above average for the next10 days in East Antarctica. The continent also has some of the largest temperature anomalies on the planet. July was substantially above average, but as we head into August, those temperatures are even more above average. Last week, temperatures were 20 degrees (12 Celsius) above average.

Record-breaking events

The South Pole Station has seen its warmest July since 2002, according to Antarctic temperature analyst Stefano Di Battista. July 2024 was 11 degrees (6.3 Celsius) above average. Between July 20th and July 30th, the average temperature was -54 degrees (-47.6 Celsius).

These are typical temperatures for the end of February, which is the end of summer in Antarctica. Vostok, located in the center of the ice sheet, will see its warmest July since 2009, at 12 degrees (6.4 Celsius) above average. This heat wave is extraordinary for a number of reasons, but especially for its duration rather than its intensity.

For the northern part of the continent, a cold snap took place earlier in July. On July 17, Dome Fuji weather stations recorded temperatures of -115.8 degrees (-82.1 Celsius), making it the second coldest July on record. Winter temperatures in Antarctica fluctuate because of the lack of sun.

Where did this heat wave come from?

It is still too early to tell the exact causes of this heat wave. This heat wave is unique because of its larger-than-normal anomaly. This can be linked to stratospheric processes more than 20 miles up into the atmosphere. The stratosphere has the polar vortex, which is a strong band of cold air that spins around the poles.

The polar vortex is stable during winter in the Southern Hemisphere. This year, the polar vortex has been bumped around by atmospheric waves, which weakens the vortex and causes high-altitude temperatures to increase drastically, says Amy Butler, an atmospheric scientist at NOAA. This is what’s 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.

A sudden stratospheric warming (SSW) event also affects the lower atmosphere where weather occurs. A weakened jet stream allows polar air to drift north towards New Zealand, southern Africa and southern South America.The cold air leaving eastern Antarctica allowed warmer air to take its place.

Multiple factors are involved

Ice cover is also at the second-lowest on record. Sea ice reflects sunlight back into space, which keeps polar regions cool. The entire planet has seen more than 1.5 degrees Celsius of warming in the last 12 months. The poles also warm at a faster rate, twice as fast in Antarctica, than the rest of the world.

Global temperatures increasing also increases the ‘baseline’ for average temperatures. Strong warming events like this one can occur more frequently and have a larger impact. The largest heat wave in Antarctica, and the entire world occurred in March of 2022. The eastern coast of Antarctica saw temperatures 70 degrees (39 Celsius) above average.