A new study in the journal Nature has found that the amount of dissolved oxygen in the ocean is declining worldwide – and it’s a direct result of climate change. The paper was authored by researchers from GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, and found that the oceans of the world have lost more than two percent of their oxygen content between 1960 and 2010. However, the losses were not spread evenly across the globe – the Arctic Ocean, in particular, has suffered the sharpest decline.
Why? Global warming. The major reason is that warm liquid holds onto dissolved gas less easily, but there are other factors at play as well. Ocean stratification is becoming a major issue – normally, oxygen enters the water at the surface and mixes down, but because warm water is less dense and doesn’t sink as rapidly, the oxygen-rich water closest to the surface simply floats instead.
None of this is news to climate scientists. In fact, climate models have predicted this effect might happen for years. However, this is the first study to look at millions of ocean measurements and combine them into a single analysis, proving the effect is actually happening.
The oceans already naturally contain “oxygen minimum zones” which can’t support much marine life, usually occupying the middle depths of the ocean. Scientists fear this shift in oxygen levels may expand those areas, and potentially create “dead zones” in shallow areas, effectively reducing the habitat available for marine organisms.
Worse yet, the situation may end up creating a feedback loop that could actually worsen climate change. These oceanic “dead zones” tend to be areas where microorganisms that produce greenhouse gasses like nitrous oxide thrive. The study is just one more piece of evidence showing that we need to take strong action to curb climate change immediately.