South Ocean as climate factor

Antarctic expedition provides new insights into the role of the Southern Ocean

Research vessel Polarstern in the Antarctic ice © AWI
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When many algae bloom in the Southern Ocean around Antarctica, it affects not only the regional ecosystems, but also the global climate. Because the algae consume the carbon dioxide from the surface water and thus enhance the buffer effect of the sea. This is one of the findings that scientists from the just completed Antarctic expedition of the research vessel Polarstern have brought.

Key region of the global climate action

On the expeditions of the German research vessel Polarstern, researchers from all over the world are doing pioneering work for the understanding of the Southern Ocean during the International Polar Year 2007/08. This huge ring ocean around the Antarctic is still largely unexplored. But because it has a decisive influence on the climate of the whole earth, an intensification of research activities is urgently needed. The International Polar Year offers a unique opportunity to pool the scientific efforts of different countries in order to collectively gain significant insights.

Melt produces fresh water layer

The now completed Polarstern Expedition of the Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association began on 28 November 2007 in Cape Town. It was mainly dedicated to the living beings and material cycles in the sea. Under the direction of Professor Ulrich Bathmann from the Alfred Wegener Institute, 53 scientists from nine countries studied, among other things, the biological carbon pump in the Southern Ocean. Plant plankton binds carbon through its photosynthetic activity, removing carbon dioxide from the atmosphere in this way.

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The researchers have discovered that melting sea ice has formed a sweeter surface lens and thus lighter water. The growing plankton bloom had already partially sunk and transported its organic material to the deep sea. At the seafloor metabolic processes were triggered. display

Algae carpet twice as big as Germany

At the edge of the sea ice, the scientists investigated an algae carpet floating in the water. This algal bloom was 700, 000 square kilometers, about twice as large as Germany. The researchers wanted to know under which physical conditions such algal blooms arise and what effects they have on both the living and the inanimate environment.

Their measurements have shown that the carbon dioxide content in surface water has decreased significantly. The measurements have also shown that the plankton blooms in the surface water have an impact on the living community on the seabed. For the first time ever, the entire water column in the Southern Ocean was simultaneously and extensively sampled from the surface to the ocean floor in the deep sea. This inventory of flora and fauna should also serve as a basis for comparison for future investigations.

International workshop on board

An international workshop on climate research in the Southern Ocean will take place on 5 February in Cape Town on board Polarstern. The scientists aboard the French research vessel Marion Dufresne and the German research vessel Polarstern meet with South African partners to exchange results and discuss future cooperation. Federal Research Minister Annette Schavan will also use the opportunity to meet with representatives of leading research institutions and South African ministerial colleagues. Already on 6th February Polarstern will leave for the next Antarctic expedition.

(Alfred Wegener Institute for Polar and Marine Research in the Helmholtz Association, 06.02.2008 - NPO)