Helmholtz Study Measures Oxygen Loss From World Oceans Over Past 50 Years - It's Global
15 February 2017 / Kiel. The ongoing global change causes rising ocean temperatures and changes the ocean circulation. Therefore less oxygen is dissolved in surface waters and less oxygen is transported into the deep sea. This reduction of oceanic oxygen supply has major consequences for the organisms in the ocean. In the international journal Nature, oceanographers of GEOMAR Helmholtz Centre for Ocean Research Kiel have now published the most comprehensive analysis on oxygen loss in the world's oceans and their cause so far.
Oxygen is an essential necessity of life on land. The same applies for almost all organisms in the ocean. However, the oxygen supply in the oceans is threatened by global warming in two ways: Warmer surface waters take up less oxygen than colder waters. In addition, warmer water stabilizes the stratification of the ocean. This weakens the circulation connecting the surface with the deep ocean and less oxygen is transported into the deep sea. Therefore, many models predict a decrease in global oceanic oxygen inventory of the oceans due to global warming. The first global evaluation of millions of oxygen measurements seems to confirm this trend and points to first impacts of global change.
In the renowned scientific journal Nature the oceanographers Dr. Sunke Schmidtko, Dr. Lothar Stramma and Prof. Dr. Martin Visbeck from GEOMAR Helmholtz Centre for Ocean Research Kiel just published the most comprehensive study on global oxygen content in the world's oceans so far. It demonstrates that the ocean’s oxygen content has decreased by more than two percent over the last 50 years. “Since large fishes in particular avoid or do not survive in areas with low oxygen content, these changes can have far-reaching biological consequences,” says Dr. Schmidtko, the lead-author of the study.
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The study also shows that, with the exception of a few regions, the oxygen content decreased throughout the entire ocean during the period investigated. The greatest loss was found in the North Pacific. “While the slight decrease of oxygen in the atmosphere is currently considered non-critical, the oxygen losses in the ocean can have far-reaching consequences because of the uneven distribution. For fisheries and coastal economies this process may have detrimental consequences,” emphasizes the co-author Dr. Lothar Stramma.
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http://www.geomar.de/en/service/kommunikation/singlepm/article/global-ocean-de-oxygenation-quantified/
