Continuously high greenhouse gas emissions could lead to long-term oxygen depletion in the global ocean, potentially with significant negative effects on fish and other marine animals for thousands of years.

Online in Nature Geoscience this week, Gary Shaffer and colleagues simulate the effects of human-induced greenhouse gas emissions with a low-complexity Earth system model for 100,000 years into the future. They evaluate two emissions scenarios ? moderate and high emissions ? used by the Intergovernmental Panel on Climate Change (IPCC). In their simulations the surface ocean loses oxygen mainly in response to warming, through a decrease in the solubility of the gas in seawater. However, the deep ocean is also affected ? a result of a slower overturning circulation, compared with today’s climate, which brings oxygenated surface waters to depth.

The researchers conclude that substantial reductions in fossil-fuel use over the next few generations are needed to avoid extensive ocean oxygen depletion.