Temperatures around the North Pole surged close to melting point on Thursday as a freak blast of warm air blanketed an Arctic region usually deep frozen in mid-winter darkness, scientists said.
Air temperatures at the North Pole were an estimated minus 4 degrees Celsius (24.8 Fahrenheit) around midday with light snow, according to the Norwegian Meteorological Institute, against a more usual temperature close to -30 degrees Celsius (-22F).
There are no weather stations at the Pole itself but a buoy floating in the Arctic Ocean north of the Norwegian island of Spitsbergen was reporting zero degrees (32F) on Thursday.
Worldwide, this year is set to be the warmest on record, driven up by man-made greenhouse gas emissions and a powerful El Nino weather event in the Pacific Ocean.
"There's a low pressure between Greenland and Spitsbergen, with a very powerful air current" driving warm air north, said Justyna Wodziczko, a Norwegian Meteorological Institute forecaster.
Such spikes in Arctic temperatures "are becoming more frequent because we have a declining sea ice cover - the water below is warmer," said Jesper Eriksen, a forecaster at the Danish Meteorological Institute.
Arctic sea ice is at a record low for the time of year, according to December 20 measurements by the U.S. National Snow and Ice Data Center.
The Arctic region is warming at twice the global average, disrupting the hunting livelihoods of indigenous people and threatening creatures such as polar bears while opening the region to more shipping and exploration for oil and gas.
The temperatures are expected to fall in coming days. The Norwegian Meteorological Institute issued a Tweet this week showing that Father Christmas's sleigh would be able to take off without a risk of getting bogged down in slush.
In late December a year ago, temperatures also briefly rose to around freezing point.
Such winter temperature surges have typically happened once or twice a decade stretching back to a first recorded event in 1959, according to a study in the journal Scientific
Reports this month by G.W.K. Moore of the University of Toronto.
Such events were expected to happen more often "as the region transitions towards the occurrence of warmer and wetter winters," he wrote.
A U.N. panel of climate scientists says it is at least 95 percent likely that man-made greenhouse gas emissions are the main cause of climate change, disrupting food and water supplies with more floods, heat waves and rising sea levels.