The sea ice at the North Pole is shrinking. Both the volume of ice in the Arctic and the area of the ocean’s surface covered by ice there have been steadily decreasing since satellite measurements began in 1979 – by more than ten percent per decade on average. Whereas the extent of Arctic sea ice totaled some 7.3 million square kilometers between 1980 and 1989, the same figure only amounted to approximately 4.2 million square kilometers in the period from 2001 to 2019. The especially thick perennial sea ice is dwindling very rapidly; as a result, the remaining ice cover is reacting ever more sensitively to warming.¹