The South Pole, the most isolated part of the planet, is also one of the fastest warming, scientists said Monday, with surface air temperatures rising since the 1990s at a rate three times faster than the global average.
While warming may be the result of just natural climate change, the researchers said, the effects of man-made warming are likely to have contributed to it.
The pole, home to a United States research base in the high, frozen void of the Antarctic interior, heated by about 0.6 degrees Celsius, or 1.1 degrees Fahrenheit, per decade over the past 30 years, researchers have reported in an article published in Nature Climate change. The global average during that time was around 0.2 degrees Celsius per decade.
By analyzing weather data and using climate models, the researchers found that rising temperatures are the result of changes in atmospheric circulation that originate thousands of miles away in the western tropical Pacific Ocean.
“The South Pole is heating up at an incredible rate and is mainly driven by the tropics,” said Kyle R. Clem, postdoctoral researcher at Victoria University of Wellington in New Zealand and lead author of the study.
While climate change resulting from emissions of carbon dioxide and other greenhouse gases has most likely played a role, analysis has shown that natural climate variability could account for all extreme temperature fluctuations, effectively masking any contributions caused by man.
“The interior of the Antarctic could be one of the few places left on Earth where the anthropogenic signal cannot be easily fooled because of such extreme variability,” said Dr. Clem.
“But it is very, very unlikely that such a warming trend will occur without increasing greenhouse gases,” he added.
Pole temperature records have been preserved since 1957, when the first American base was completed there. For decades, average temperatures have been constant or falling. The strong western winds that surrounded the continent served as a barrier, preventing warmer air from entering the interior.
But that changed towards the end of the 20th century, said dr. Clem, when sea surface temperatures in the western tropical Pacific began to rise, part of a natural swing that occurs on a time scale of decades.
The warming ocean heated the air, causing ripples of high and low pressure in the atmosphere that reached the Antarctic Peninsula, over 5,000 miles away. Scientists call this type of long distance link teleconnections.
Together with the stronger westerly winds, which are part of another long-term pattern, the ripples led to stronger storms in the Weddell Sea, east of the peninsula. These rotating, or cyclonic, storms swept warmer air from the southern Atlantic Ocean into the interior of the continent.
Heavy storms in the Weddell Sea have also led to recent decline of sea ice in the region.
Dr. Clem said the warming was not uniform across the Antarctic Plateau, the huge expanse that covers most of the interior, including the pole, with an average altitude of almost two miles. But the only other permanent base on the plateau, the Russian station Vostok about 800 miles from the pole, has also experienced rapidly rising temperatures, he said.
Ripples in the tropical Pacific also had an effect on the Antarctic Peninsula, which for most of the late 20th century had been one of the fastest warming areas in the world. But in recent decades, the warming rate has dropped significantly.
In an email, two researchers from the University of Colorado, Sharon E. Stammerjohn and Ted A. Scambos, said that while the rest of the world has steadily warmed up over the past fifty years, Antarctica has seen large swings. , and probably always has. Neither scientist was involved in the research, but they wrote a comment on the study published in the same issue of the journal.
As ocean temperatures in the tropical Pacific shift towards cooling, they said, the rate of warming at the South Pole will also likely decrease, but not as much as it would have without man-made climate change.
In an interview, Dr. Stammerjohn said that “warming at the South Pole is significant because it is the most remote place on the planet.”
“But it will never get through the freeze,” he said. “We don’t have to worry too much about losing ice at the stake yet. But the shores are definitely another thing.”
Especially along the coast of western Antarctica, the warm water raised by the depths of the wind is melting the ice shelves from below, which ultimately leads to sea level rise.
Dr. Stammerjohn said there was increasing evidence that the way the planet is responding to warming was changing the atmosphere and ocean circulation on a large scale.
“And that’s what is contributing to the warmer waters in depth,” he said. “There will be a lot of variability superimposed on this, but the direction, and the projection, would be towards more and more hot water and more ice sheet loss.”
“It’s so easy to think that Antarctica is isolated and remote and won’t respond to climate change,” said Dr. Stammerjohn. While the impact on the South Pole may not be as significant, the ice loss along the coast has huge implications.
“It’s what will drastically change our sea level,” he said.
Heating to the South Pole, he said, is “the last canary in the coal mine, one that we can no longer ignore.”