These unseasonably warm weather patterns in the Arctic region are directly linked to man-made climate change, they said.
Temperatures throughout November and December this year were five degree Celsius higher than average. It follows a summer during which Arctic sea ice reached the second-lowest extent ever recorded by satellites.
"In pre-industrial times, a heatwave like this would have been extremely rare - we would expect it to occur about every 1,000 years," said Friederike Otto, a senior researcher at Oxford University told 'BBC News'.
Forecasting models show that there is about a 2 per cent chance of a heatwave event occurring every year. "But if temperatures continue to increase further as they are now, we would expect a heatwave like this to occur every year and that will be a huge stress on the ecosystem," said Otto.
The freeze and thaw conditions are already making it difficult for reindeer to find food - as the moss they feed on is covered by hard ice, rather than soft, penetrable snow.
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