Feb. 15 (UPI) -- The scientific logic of ocean de-oxygenation is well established, but few studies have attempted to quantify the global loss of oxygen in Earth's oceans.
Scientists at the GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, set out to do just that. Their findings, detailed in the journal Nature, suggest ocean oxygen levels are shrinking across the globe.
Global warming has accelerated the rise of ocean surface temperatures. Warmer water absorbs less oxygen than cold water. Warming in the ocean also yields stratification and diminishes upwelling and vertical currents. Less mixing means the deep ocean gets supplied with less oxygen from the surface.
A few studies have modeled the rise in ocean temperatures and resulting loss of oxygen on a small scale.
"To quantify trends for the entire ocean, however, was more difficult since oxygen data from remote regions and the deep ocean is sparse," oceanographer Sunke Schmidtko said in a news release. "We were able to document the oxygen distribution and its changes for the entire ocean for the first time. These numbers are an essential prerequisite for improving forecasts for the ocean of the future."
Researchers built a global model using historic oxygen data as well as modern ocean observations. Their analysis showed oxygen levels have been significantly diminished in all parts of the planet's oceans over the last 50 years. The loss of oxygen has been most severe in the North Pacific.
Scientists say it's possible the global loss of oxygen over the course of five decades could be the result of natural causes, but it is also in agreement with predictions of climate change models.
Scientist hope their efforts inspire improved oxyge-loss models, as the shifting distribution of oxygen in Earth's oceans will have a dramatic effect on a variety of marine biochemical systems.
"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," said researcher Lothar Stramma. "For fisheries and coastal economies this process may have detrimental consequences."