A study published in the journal Nature last month provided a comprehensive picture of the extent of oxygen reduction in the world’s oceans. Researchers from the GEOMAR Helmholtz Center for Ocean Research found that between 1960 and 2010, the oceans as a whole lost more than 2 percent of their oxygen, the Washington Post reported.
But the decline isn’t the most intriguing conclusion from the research: Ocean oxygen loss has been a long-predicted effect of climate change, partly because warmer water can hold less dissolved gas.
Less ocean circulation drives oxygen loss
A large portion of the loss, the study concluded, can be attributed to reduced mixing of ocean waters. The increasing temperature of surface waters – where oxygen enters the ocean from the atmosphere or photosynthesizing organisms – means that these comparatively oxygen-rich waters do not mix as readily with deeper, colder ocean water.
According to the study, only 15 percent of ocean oxygen loss could be directly attributed to warmer waters. Reduced circulation and other factors played bigger roles.
The study was based on “millions of measurements,” which the authors say show that oxygen loss is worse in some places than others. While the North Atlantic fared relatively well, the North Pacific saw the most oxygen escape and the Arctic Ocean – which has endured off-the-charts temperatures this winter – lost the greatest percentage.
Ocean ecosystems changing rapidly
Oceans have already absorbed about 40% of the carbon dioxide emitted by humans. As ocean carbon dioxide increases while oxygen decreases, the entire spectrum of marine life will feel the consequences. Risk factors will increase for hypoxic zones, which kill or drive away all oxygen-breathing life and allow anaerobic bacteria to proliferate.
Research such as this tells us that the changing climate is impacting parts of the globe differently. Climate change will have effects more complex, localized, and extreme than uniform temperature increases.
Further study of ocean health is needed
Unfortunately, this study relied on incomplete data to reach its conclusions, using interpolation techniques to fill in holes. The oceans are vast, and not every area is being well-documented. The oceans at the poles are being most affected by climate change, but are among the least studied.
More data collection is needed to paint a better, more reliable picture of our changing oceans. Human health and livelihood, not to mention the world’s largest ecosystem, is at risk. PME is proud to be on the front lines of tracking these changes with durable long-term data loggers and other monitoring equipment.