Since the last Polarstern expedition to the region, in 2018, measuring devices anchored to the seabed have been recording the temperature and salinity, as well as the strength and direction of the currents, at various depths. To access the data, the devices now have to be retrieved. Then, outfitted with new batteries and memory cards, they will be returned to the ocean floor to resume their long-term recording of oceanographic parameters.
The target region is not only vital for global deep-water formation, but is also one characterised by intensive algal blooms, especially in the summer months. “Accordingly, during the expedition we will be investigating how much of the atmospheric carbon is taken up by phytoplankton in surface waters, what fraction of the algae bloom later sinks down from the surface, and how much additional carbon is exported from the continental shelf to the deep sea as a result of deep-water formation,” explains Dr Moritz Holtappels, a biogeochemist at the Alfred Wegener Institute. The transport rates of this bio-physical carbon pump depend not just on the sea-ice cover, but also on the availability of nutrients and trace metals, which determine the growth and composition of the algal communities and their predators. The carbon pump delivers nutrients to the depths, making it an essential lifeline for the unique fauna of the Southern Ocean sea floor. In addition, the research conducted on the carbon cycle will seek to identify how the pump influences the distribution and diversity of the fauna, and to assess the importance of these ocean regions and the life in them as a sink for atmospheric carbon.