Can the ocean freeze

Warm pincer grip: Why the Arctic Ocean isn't freezing over right now

Although the arctic winter has long since set in, the ocean is not freezing over. Almost a million square kilometers of ice are currently missing compared to October 27, 2016 - when experts determined the lowest ice cover ever recorded on the date. As recently as last week, the deficit was only a little more than half that. The values ​​show: At a time when the ice surfaces should actually increase rapidly, the water remains open. This applies above all to the ocean off Siberia; practically no new ice is currently forming there.

According to Mark Serreze, director of the National Snow and Ice Data Center in the United States, the cause of the problem is that the ocean has stored much more heat than usual. In the first half of 2020, a heat wave in Siberia melted the sea ice unusually early; bright, reflective ice disappeared, revealing dark water, which absorbs the sun's heat much better. At the same time, relatively warm Atlantic water, which was previously isolated in the depths, has been rising closer to the surface for years. The sea ice is stuck in a warm pincer grip from above and below.

Both effects are part of a vicious circle that has been going on for years, in which the lack of sea ice favors warmer water - which in turn prevents the ocean from freezing over. Not only does less ice cover the sea, it is also thinner and therefore less stable. As a result, it not only melts faster in spring, it is also vulnerable to the stronger waves that form on the ever larger open water areas.

The open, warm water also warms the land. There the snow-covered area has been decreasing significantly for decades, especially in summer - and like the sea, the land is darker than the snow and absorbs sunlight better. Warm land areas, in turn, favor earlier ice melt on the water. These trends mean that there is a high probability that the Arctic will be completely free of sea ice by the middle of the century. An ice-free Arctic, in turn, warms the entire planet - by around half a degree more, as a working group calculated in a recent publication.