The coldest location on the planet has experienced an episode of warm weather this week unlike any ever observed, with temperatures over the eastern Antarctic ice sheet soaring 50 to 90˚F (28 to 50˚C) above normal. The warmth has smashed records and shocked scientists.
“This event is completely unprecedented and upended our expectations about the Antarctic climate system,” said Jonathan Wille, a researcher studying polar meteorology at Université Grenoble Alpes in France.
Instead of temperatures being -50 or -60˚F (-45 or -51˚C), they’ve been closer to zero or 10˚F (-18 or -12˚C).
The average high temperature in Vostok — at the center of the eastern ice sheet — is around -63˚F (-53˚C) in March. But on Friday, the temperature leaped to zero (-17.7˚C), the warmest it’s been there during March since record keeping began 65 years ago. It broke the previous monthly record by a staggering 27˚F (15˚C).
“Antarctic climatology has been rewritten,” tweeted Stefano Di Battista, a researcher who has published studies on Antarctic temperatures. “In about 65 record years in Vostok, between March and October, values above -30°C were never observed,” wrote Di Battista.
Temperatures running at least 50˚F (32˚C) above normal have expanded over vast portions of eastern Antarctica from the Adélie Coast through much of the eastern ice sheet’s interior.
Wille said the warm conditions over Antarctica were spurred by an extreme atmospheric river, or a narrow corridor of water vapor in the sky, on its east coast. According to computer models, the atmospheric river made landfall on Tuesday between the Dumont d’Urville and Casey Stations and dropped an intense amount of rainfall, potentially causing a significant melt event in the area.
The moisture from the storm diffused and spread over the interior of the continent. However, a strong blocking high pressure system or “heat dome,” moved in over east Antarctica, preventing the moisture from escaping. The heat dome was exceptionally intense, five standard deviations above normal.
The excessive moisture from the atmospheric river was able to retain large amounts of heat, while the liquid-rich clouds radiated the heat down to the surface — known as downward long-wave radiation.
Wille explained warm air is often transported over the Antarctic interior this way but not to this extent or intensity. “This is not something we’ve seen before,” he said. “This moisture is the reason why the temperatures have gotten just so high.”
The historically high temperatures in Antarctica follow a pulse of exceptional warmth on the planet’s opposite end. On Wednesday, temperatures near the North Pole catapulted 50˚F (28˚C) above normal, close to the melting point.