In the Arctic, it is on average 20°C warmer than seasonal norms, unheard of. At a time when the sea ice should be expanding, it has contracted under the effect of exceptional mildness. As a direct consequence, the extent of the sea ice has never been so small since the start of the measurements and has recorded a delay of 2 million km² compared to the 1981-2010 average.
Are we heading towards the death of winter in the Arctic? In November the sea ice is in the middle of the polar night with 24 hours of darkness each day. Temperatures are expected to be plunging, and sea ice expanding. Instead, temperatures are soaring, and the ice continues to shrink. As shown by the curve presented below, published by the Danish Meteorological Institute, in certain areas, the air temperatures measured reached -5°C, instead of -25°C usually on the same date in month of November.
“Such temperatures in October and November have never been recorded in 68 years of measurements”, explains Jennifer Francis, climatologist at Rutgers University (United States), in an article by Climate Central. A complex set of factors seems to be at play, but it seems that unusual meteorology and the weakening of the pack ice partly explain this anomaly observed in the Arctic.
As Ted Scambos, principal investigator at the National Snow and at Ice Data Center, two major storms recorded last August in the region helped break up sea ice, stirring up warmer waters from the depths. This implies that large areas of the ocean surface have been exposed to sunlight for a longer than normal period of time. But while ice is known to reflect sunlight, darker surface waters easily absorb it. Thus, the water already warmed by the stirring action of the storms was able to warm further, thus preventing the formation of sea ice.
Today part of this absorbed energy is returned to the atmosphere, and at the same time, an unusual atmospheric circulation has favored southerly winds in certain sectors, thus explaining the recorded surface temperatures. It should also be noted that at the other pole, in Antarctica, sea ice is also recording historically low levels.
Surprising time-lapse of the evolution of the sea ice between late March and mid-August 2016.