As a result of a detailed analysis of the composition of marine sediments, scientists proved that the Arctic Ocean did not contain sea salt: at least during two ice ages.

Instead of sea salt, the Arctic Ocean, like the North Seas, was filled with large amounts of freshwater under a thick ice sheet.

This water probably entered the North Atlantic: such a sudden influx of freshwater could explain the rapid fluctuations in climate, for which no explanation had previously been found.

About 60–70 thousand years ago, during the particularly cold part of the last ice age, most of Northern Europe and North America was covered with ice sheets.

The European ice sheet stretched over 5,000 km from Ireland and Scotland. In North America, much of what is now Canada was buried under two large ice sheets. Greenland and part of the Bering Sea coastline were also covered in ice. However, it was not previously known what the Arctic Ocean was like during this period.

So far, only a few traces of extensive ice shelves have been found in the Arctic Ocean. Geological scientists from the Alfred Wegener Institute, the Helmholtz Center for Polar and Marine Research (AWI), and the MARUMA Center for Marine Environmental Sciences at the University of Bremen have now collected existing data on the Arctic Ocean and the North Seas and combined them with new research.

The find is based on geological analyzes of ten sediment cores from different parts of the Arctic Ocean. According to their research, floating parts of the northern ice sheets have covered most of the Arctic Ocean over the past 150 thousand years. During both periods, freshwater accumulated under the ice for thousands of years.