The research vessel Polarstern returned to Bremerhaven from a four-month expedition on Saturday, 9 October. On its 25th mission in the Arctic the ship covered a total of around 16,620 nautical miles (corresponding to about 30,780 kilometres). The focus of the three legs was on oceanographic, biological and geoscientific studies. Over 120 scientists and technicians from institutes in six nations took part in the expedition.
The Polarstern launched its journey from Bremerhaven on 10 June, heading for the Greenland Sea. This is an important area for the formation of deep water that thus ensures thorough mixing of the ocean and drives global marine currents. The crew under chief scientist Dr. Gereon Budéus from the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association picked up instruments that were installed 3.7 kilometres deep in the central Greenland Sea. The measuring devices at these moorings recorded the temperature and salinity of the water for more than a year. “This hydrographic work forms a major piece of the puzzle with regard to our long-term series of tests over a period of ten years, which are indispensable for climate-related research,” explains Budéus.
After a brief change in staff in Longyearbyen (Spitsbergen) the vessel headed to the Fram Strait, the marine region between Spitzbergen and Greenland, and to the so-called HAUSGARTEN, a deep-sea long-term observatory on the continental slope west of Spitsbergen run by the Alfred Wegener Institute for over ten years now. There chief scientist Dr. Thomas Soltwedel and his team documented how changing climate conditions influence the marine Arctic ecosystem. Biologists and oceanographers examined over 160 stations altogether, both here and in the expedition’s second area of study, a hydrographic transect across the Fram Strait. A chain of moorings across the Fram Strait that has been monitoring the exchange between the North Atlantic and the Arctic Ocean for 15 years was replaced so that the changes in temperature and salinity can continue to be followed next year. A highlight of the second leg was the first under-ice mission for the autonomous underwater vehicle (AUV) of the AWI deep-sea group. The unmanned AUV is equipped with various sensor systems and sampling devices. It supplies valuable information on physical, chemical and biological parameters in the ecologically important transition zone between the ice-covered ocean and its ice-free margins.
The third leg focused on geoscientific topics. Due to an internal Canadian conflict involving the procedure for research approval, the work had to be restricted to Greenland waters. The Polarstern sailed north beyond the 80th degree of latitude for this purpose. The team under chief scientist Dr. Volkmar Damm from the Federal Institute for Geosciences and Natural Resources was able to research areas in the Nares Strait, in which the available database has been very fragmentary up to now due to sea ice conditions. “The currently available results show the Greenland portion of Baffin Bay to be a typical passive continental margin with perturbations towards the sea and deep basin structures with thick sediment strata,” reports Damm. The geophysicists reveal new findings on the structures of the deeper subsoil of Baffin Bay and the characteristics of the sediments and their content of microbial communities. On this basis, researchers can better reconstruct the geological past of Baffin Bay and the deposition history of the sediments in this Arctic marginal sea. The results are important, among other things, for an understanding of palaeological changes and the microbial decomposition of organic material under polar conditions. For Captain Uwe Pahl sailing through Nares Strait and Smith Sound was a highlight of the expedition. “The relatively narrow strait between northeast Canada and Greenland’s westernmost point requires concentrated navigation to use all scientific equipment securely.”
Even though the scientific questions and thus the technical requirements of the three legs varied greatly, all chief scientists agreed on one point: the working conditions onboard Polarstern are outstanding because of the optimal cooperation between the crew and scientists.
The Alfred Wegener Institute conducts research in the Arctic, Antarctic and oceans of the high and mid latitudes. It coordinates polar research in Germany and provides major infrastructure to the international scientific community, such as the research icebreaker Polarstern and stations in the Arctic and Antarctic. The Alfred Wegener Institute is one of the sixteen research centres of the Helmholtz Association, the largest scientific organisation in Germany.
Margarete Pauls | idw
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