Climate change is doing more than warming the world’s oceans. It’s also making it harder for marine life to breathe.

Curtis Deutsch, associate professor at the University of Washington’s School of Oceanography, studies how increasing global temperatures are altering the levels of dissolved oxygen in the world’s oceans. Scientists have been warning that decreasing amounts of available oxygen will increase stress on a range of species, even as they also face the effects of rising temperatures and ocean acidification.

Deutsch’s latest research is untangling how much oxygen loss is linked to climate change and how much is due to normal variation in oxygen levels.

“As the climate goes up, the amount of oxygen will go down, but it’s really hard to look in the ocean to see that change,” he said.

Using an earth system modeling approach, Deutsch and scientists at the National Center for Atmospheric Research and the Georgia Institute of Technology mapped out changing oxygen levels across the world’s oceans through the end of the 21st century.


New research from the National Center for Atmospheric Research finds that ocean deoxygenation will likely become widespread between 2030 and 2040. Other parts of the ocean, shown in gray, will not have detectable loss of oxygen due to climate change even by 2100.
Graphic courtesy of Matthew Long, NCAR.


They found that it was possible to distinguish the impact of global warming from other sources of oxygen loss. As soon as 2030 to 2040, climate-driven declines in oxygen levels will be detectable in oceans all over the globe. In some places, like the southern Indian Ocean and parts of the eastern tropical Pacific and Atlantic basins, evidence of climate-linked deoxygenation is already apparent, while other regions won’t see changes by 2100.

The researchers recently published their results in Global Biogeochemical Cycles.

“In some parts, you can actually detect a change relatively early, like right around now. The signature of the climate being warmer is creating something that is unlike anything that is seen in history. Other places it is much harder to detect, either oxygen is decreasing slowly or there is so much [natural] variation. So basically the results depend on where you are,” Deutsch said.


The influence of climate change was evident in areas with either extreme incidents of oxygen depletion or longer-than-normal trends of low oxygen levels. Places like the southern Indian Ocean that showed the strongest warming signal the soonest tend to be the areas that will see the worst affects of warming, he explained.

Those changes have a significant impact on a wide range of marine life.

“Oxygen is playing a fundamental role in where species can live or not live,” he said.