Oxygen (O₂) is essential for nearly all multicellular life. Subsurface oxygen concentrations reflect a balance between supply through circulation and ventilation and consumption by respiratory processes. Changes in either of these processes is susceptible to lead to changes in O₂ distribution. A global ocean O₂ observing network will act as a sensitive early warning system for trends that climate change is causing. Ocean deoxygenation (decline in O₂ concentration) is under way in part because of ocean warming and increased stratification, but also because of increased nutrient loads in the coastal ocean. Deoxygenation has been largely under the radar to most people including policy advisers and decision makers. Yet it is deoxygenation that will have profound implications not just for ecosystems but also for communities and economies that depend on a healthy ocean. It is one of the prices we are now paying for the fact that the ocean has been shielding us from the worst effects of climate change which would otherwise have resulted from the continuing excessive emissions of carbon dioxide and other greenhouse gases. 

To find out about IOCCP's role in coordinating global ocean O₂ observations, click on the Current IOCCP Activities tab below.

Changes in ocean oxygen content

(left) Global map showing coastal sites (purple dots) and open ocean sites (red to yellow, at 300 m of depth) where O₂ levels are below 2 mg-L^-1 (Adapted from Breitburg et al., 2018). (right) Change in oxygen content of the global ocean in mol-O₂ m^-2-decade^-1. (From Breitburg et al., 2018)