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Polar regions normalise – for now – after record-breaking heat

Temperatures have returned to normal at the poles since the extreme heat recorded last month but scientists remain deeply worried about the future of the Earth’s polar regions.

The planet’s poles made international headlines mid-March amid unprecedented heatwaves. Temperatures 30 to 40 degrees Celsius (54-72F) above average were recorded in both the Arctic and Antarctic.

On Friday March 18, the Concordia research station – located 3,200 metres (10,500 feet) above sea level in the heart of Antarctica – registered an all-time high of -11.8C (110.8F), 40C above seasonal norms.

In parallel, Russia’s Vostok station in East Antarctica broke its previous record for the month of March of -32.7C (-26.9F), reaching -17.7C (0.1F).

Meanwhile, some parts of the Arctic warmed to 30C above average.

The twin events helped make last month the fifth-warmest month of March on record and rang as a warning bell – could climate be breaking down faster than projected?

‘Exceptional’ heat
One month on, scientists remain shocked by the intensity of March’s events, which follow several alarming heatwaves in the summer of 2021.

Last July, temperatures peaked to nearly 50C (122F) in the United States’ Pacific Northwest. In the Antarctic, Concordia station also broke a winter record as temperatures reached -26.6C (15.9F), about 40C above normal.

“Strongly fluctuating temperatures are something we traditionally witness in Antarctica, and are not exceptional. What was exceptional is the magnitude of this event,” astrophysics professor Tristan Guillot from the French national research centre CNRS told Al Jazeera.

Guillot and his team, who analyse data provided by the Concordia station, were in the front row to observe the unprecedented polar heat.

Antarctica is entering autumn and temperatures should have been decreasing sharply since December 21. Still, “this peak in inland temperature had little impact in practice”, Christophe Genthon, a research meteorologist at CNRS, highlighting the “temperature remained well below anything that would have allowed the ice to melt”.

Concordia and Vostok stations are located deep within the Antarctic continent and sit on more than three kilometres (1.2 miles) of ice – which have been piling up there across thousands of years, in a part of the continent that has been surprisingly protected from warming temperatures.

“Climate has remained remarkably stable in East Antarctica over the past years compared to West Antarctica, which has warmed up markedly,” Genthon told Al Jazeera.

There are many possible reasons for this. Some scientists point to the natural variability of weather in East Antarctica, which could have “buffered” global warming trends, or to the recovery of the ozone layer thanks to the adoption of the Montreal protocol in 1989, which bans the use of certain products responsible for ozone depletion. The ozone layer plays an important role in blocking out the sun’s ultraviolet radiation, which warms up the atmosphere.

Peter Neff, a glaciologist and assistant research professor at the University of Minnesota, said, “One of the reasons that Antarctica is not warming as strongly as many places on the planet is that it’s so big and it has such steep margins that it keeps a lot of that heat out.”

But with warming temperatures in the Southern Ocean off the Australian coast, analysts expected to see more warm flows of air coming into Antarctica, and possibly more heat waves.

The temperature spike in Antarctica was caused by an “atmospheric river”, Neff told Al Jazeera, “a channelised stream of moisture that sort of gets pinched between a high and a low-pressure system”.

Atmospheric rivers gather water vapour in moist and warm regions, carry it for thousands of kilometres, and drop it in the form of rain and snow as they cool down in colder regions.

“It actually did us a favour this time in that the snowfall carried by the atmospheric river over East Antarctica added about 69 gigatons of ice volume back onto the ice sheet,” Neff said. “This means some of that ice we’re losing every year in the ocean can jump back on the ice sheet in a big snowfall event.”

That is a significant, albeit insufficient, chunk of the 150 gigatons of ice lost every year on average in Antarctica.

Still, the March incidents were not entirely without effect. In Dumont d’Urville, located off the coast of East Antarctica, unusual heat and rain were recorded.

“Rain is not exceptional on the Antarctic coast but it is rare, particularly in March, and can have important impacts on wildlife and on the stability of the Antarctic ice cap with potentially global consequences,” Genthon said.

Rising heat was also likely responsible for one of the most significant ice shelf collapses in Antarctica since the early 2000s. The Conger ice shelf, made of interlinked ice sheets covering 1,200sq km (463.3sq miles) of sea on the edges of East Antarctica, shattered on March 15, three days before the peak recorded in Concordia. Although it had been shrinking since the mid-2000s, the heat wave was likely the “final straw” for Conger.

This is significant because ice shelves play a key role in restraining the huge ice volumes piled on Antarctica from slipping into the sea. Further collapses could let huge glaciers plunge into the water, which would have a much greater impact on global sea levels.

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