From: Helmholtz Centre for Ocean Research Kiel (GEOMAR)
Published September 5, 2017 12:13 PM

Taking a deep breath?

The Labrador Sea in the North Atlantic is one of the few areas in the world ocean where cold, saline seawater sinks to large depths and forms deep water. This convection process also transports oxygen into the deep sea. A team of scientists from Scripps Institution of Oceanography (San Diego, California), Dalhousie University (Halifax, Canada) and GEOMAR Helmholtz Centre for Ocean Research Kiel have now published the analysis of data obtained from the mooring K1 in the international scientific journal Geophysical Research Letters. The results show that in winter 2014/2015 an unusually high amount of oxygen was absorbed by the ocean in the region. The actual oxygen uptake at the sea surface is very difficult to determine directly, but the scientists were able to derive the oxygen uptake from the oxygen content measured throughout the water column. One of the questions the scientists were concerned with: Can the strong oxygen uptake in the Labrador Sea compensate the global oxygen loss of the ocean?

The ocean surface, in constant gas exchange with the atmosphere, takes up oxygen from it. "In the ocean, in particular the temperature and air bubbles influence the oxygen uptake," says Dr. Johannes Karstensen, oceanographer at GEOMAR and co-author of the study. If the ocean surface cools down, the water mass becomes denser and heavier. Thus, the water mass starts to sink to greater depth, including the absorbed dissolved oxygen. At the same time, water rises from deeper layers and gets enriched with oxygen again." Sometimes this process is compared to a waterfall but in reality it is somewhat different," says Dr. Johannes Karstensen. "It is rather a re-layering where cooler, denser water sinks and the underlying lighter water rises, is then cooled down, sinks again, and so on".

Read more at Helmholtz Centre for Ocean Research Kiel (GEOMAR)

Image: Long-term observing station K1 in the Labrador Sea. (Credit: Graphics: GEOMAR)


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