For the first time, the researchers were also able to conduct large-scale investigations of the biological communities living directly on the lower side of the Arctic pack ice, with the help of a new type of under-ice trawl. "We had a polar cod in our net almost every time. This species is particularly adapted to life below the ice - it does not occur without ice." Dr. Hauke Flores explains the importance of sea ice as a habitat; she is in charge of this research topic at AWI. Sea ice physicists from AWI even used an under-ice robot to record the light incidence and algae distribution on the lower side of the ice. They detected the diatom Melosira artica in high concentrations. These single cell algae produce metre-long chains and form dense accumulations beneath the ice. Photos from the deep sea have shown that these algae drop to the bottom of the sea as a result of the melting ice.
According to the AWI researchers, the rapid changes in the Arctic are therefore not restricted to the sea surface. Atlantic water flowing into the Arctic at a depth of several hundred metres has an elevated temperature and salinity which could be measured down to a depth of several thousands of metres in the Arctic Basins. Images and measurements of the bottom of the sea showed that the deep sea of the Central Arctic is not a desert, but that sea cucumbers, sponges, feather stars and sea anemones gather to feed on the sea algae.
The warm temperatures, the retreat of the ice and the greater light availability beneath the ice causes the seasonality of the Central Arctic to shift. The production and the export of algae is taking place earlier, as the results of annually anchored sediment traps show. Due to the very thin ice cover, the Polarstern was able to navigate further North and later in the year. Hence the sea ice physicists were able to collect important data at the start of the freezing period. These measurements on the newly formed thin ice are important because this type of sea ice will occur more frequently in the future.
The "Polarstern" | in the Central Artic Ocean
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and in the high and mid-latitude oceans. The Institute coordinates German polar research and provides important infrastructure such as the research icebreaker Polarstern and stations in the Arctic and Antarctic to the international scientific world. The Alfred Wegener Institute is one of the 18 research centres of the Helmholtz Association, the largest scientific organisation in Germany. (© Alfred Wegener Institute for Polar and Marine Research AWI / AcademiaNet)