What caused this phenomenon is less surprising: scientists said oceans' oxygen loss may be a result of climate change, which now threatens marine organisms all around the world. Warm air at the surface will have a tendency to sit there, blocking off lower waters from exposure to oxygen in the atmosphere and decreasing circulation. As warmer air warms the ocean surface, the seas become less able to absorb and keep oxygen.
But, he warned, "the implications of this for marine ecosystems could be severe in parts of the ocean where oxygen is already low".
"When the upper ocean warms, less water gets down deep, and so therefor, the oxygen supply to the deep ocean is shut down or significantly reduced", Schmidtko told The Washington Post. You might not be aware of some of the many associated side effects, for instance, the fact that our oceans have been losing oxygen over the past few decades. The rest was due to more complex processes, including new oxygen not circulating all the way to the ocean's depths. However, researchers were unable to quantify just how much.
The new paper, published by climate and marine scientists at the GEOMAR Helmholtz Centre for Ocean Research in Germany, concluded that the ocean's dissolved oxygen content has declined 2 percent globally, with the Pacific and Arctic Oceans experiencing the sharpest drops. Assembling millions of ocean oxygen measurements, a team of oceanographers has found that underwater oxygen levels have already dropped an average of 2 percent worldwide since 1960.
"To quantify trends for the entire ocean, however, was more hard since oxygen data from remote regions and the deep ocean is sparse", oceanographer Sunke Schmidtko said in a news release.
Other factors which contributed to the oxygen decline are also driven by climate change; the fact that the ocean is becoming more layered leads to uneven distribution, with different depths holding different temperatures.
A few studies have modeled the rise in ocean temperatures and resulting loss of oxygen on a small scale.
Global warming has accelerated the rise of ocean surface temperatures.