Searching for traces off West Africa

Researchers are exploring the oxygen minimum zone in the Atlantic

The 95 meter long German research vessel MARIA S. MERIAN. © IFM-GEOMAR
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A sea area off the coast of West Africa in which oxygen is unusually scarce is the focus of a new expedition to which the German research vessel MARIA S. MERIAN set off from the Azores on 1 November 2008. As part of their 5-week journey, the scientists want to investigate, among other things, the circulation and mixing in the ocean.

Suspicion is mounting: warming, sea-level rise and acidification of the oceans are not the only impacts that climate change has on the oceans. More and more studies suggest that even areas where water is lacking vital oxygen, become significantly larger.

Oxygen minimum zone in sight

One of these so-called oxygen minimum zones is located in the Atlantic at the height of Senegal and Guinea. It is currently the destination of Kiel oceanographers on board the research vessel MARIA S. MERIAN. "In the tropical North Atlantic we can ideally observe the development of such oxygen minimum zones, which represent a hitherto underestimated and hardly explored danger to the oceans, " says Professor Martin Visbeck of the Leibniz Institute for Marine Sciences (IFM-GEOMAR), the expedition's leader.

As soon as the scientists arrive in the study area, they begin their search for their own traces. As early as April 2008, a Kiel expedition had worked south of the Cape Verde Islands. At that time, the researchers had used a special device, the Ocean Tracer Injection System (OTIS), a non-toxic chemical marker substance at about 300 meters depth.

Turbulence in the water column?

During the current research voyage, oceanographers want to find out where this substance has been driven in the past seven months. According to the scientists, this leads to conclusions about the mixing of the water layers, to currents and thus also to nutrient and oxygen transports. Further measurements with a falling microstructure probe are also planned and will provide information on turbulence in the upper 400 meters of the Atlantic water column. display

MERIAN's tenth expedition ends on December 6, 2008, when the ship moored in the port of Mindelo on the Cape Verde Islands.

In April 2008, the Kiel scientists introduced the Ocean Tracer Injection System (OTIS) into the Atlantic Ocean. Now they are investigating where these substances were driven. M. Muller / IFM-GEOMAR

Third research trip

The current expedition is the third exit of the Kiel Collaborative Research Center "Climate Biogeochemical Interactions in the Tropical Ocean". Scientists from IFM-GEOMAR and the University of Kiel (CAU) want to explain in the program, among other things, how tropical oxygen minimum zones (SMZ) react to changes in ocean circulation and deep ocean ventilation or which Consequences have changed oxygen levels for the nutrient supply and thus for marine life in the tropical ocean.

Also involved in the expedition is the Kiel Cluster of Excellence "Ocean of the Future". Around 120 scientists from 26 institutes of the University of Kiel, the IFM-GEOMAR, the Institute for the World Economy (IfW) and the Muthesius Academy of Fine Arts research there. The objectives of the Cluster of Excellence are to further explore the ocean change in order to develop a global management of oceans and marine resources.

(idw - Leibniz Institute for Marine Sciences, 11.11.2008 - DLO)