Temperatures at the north pole soared more than 20C above average on Sunday, crossing the threshold for ice to melt.

Temperatures north of Svalbard in Norway had already risen to 18C hotter than the 1991–2020 average on Saturday, according to models from weather agencies in Europe and the US, with actual temperatures close to ice’s melting point of 0C. By Sunday, the temperature anomaly had risen to more than 20C.

“This was a very extreme winter warming event,” said Mika Rantanen, a scientist at the Finnish Meteorological Institute. “Probably not the most extreme ever observed, but still at the upper edge of what can happen in the Arctic.”

“This type of event is relatively rare, but we are not able to assess its frequency without further analysis,” said (Julien Nicolas, a scientist at the EU’s Copernicus Climate Change Service). “We are aware that a similar event occurred in February 2018.”