The researchers detected significant differences in places where ice was lacking this summer in the Laptev Sea, for example. "On our expedition in 2007 we encount-ered thin, newly formed ice in the Laptev Sea in September. This time, however, there was no sign of ice formation anywhere. The water temperature at a depth of ten metres was three degrees Celsius that is how much the sun had heated the ice-free water surface," says Prof. Dr. Ursula Schauer, scientific head of the leg through the central Arctic. However, this warming is restricted only to the top layers. In the depths of the Arctic Ocean colder water from the Atlantic currently provides for falling water temperatures.
The sea ice physicists also made major advances in connection with the question of how much sunlight penetrates through the ice. For this purpose they utilised for the first time an underwater vehicle with remote control via cable. The so-called ROV (Remotely Operated Vehicle) dived to a depth of 100 metres below the ice and made large-scale recordings of the distribution of sunlight under the ice using a spectral radiometer. "Our measurements have shown that the quantity of light under the ice depends to a considerable extent on the type of ice. Several-year-old ice lets the least amount of light through because it has few melt ponds and a thick layer of weathered ice on its surface," says Nicolaus. One-year-old ice, by contrast, is more pervious to light, especially in areas with many melt ponds. The researchers measured the greatest amounts of light under new ice. "From these results we can conclude that the observed change from a several-year-old ice cover to a seasonal Arctic ice cover will lead to an increase in light in the Arctic Ocean, particularly in summer and a
|Contact: Sina Loeschke|
Helmholtz Association of German Research Centres