Ocean deoxygenation: everyone’s problem. Causes, impacts, consequences and solutions

Summary • The global oxygen inventory has decreased by ~2% over the period 1960 to 2010, this finding is supported by time series data that indicate a continuous decrease in oceanic dissolved oxygen. • Ocean model simulations predict a decline in the dissolved oxygen inventory of the global ocean of 1 to 7% the year 2100, caused by a combination of a warming-induced decline in oxygen solubility and reduced of the deep ocean. • Open-ocean deoxygenation is resulting mainly from a warming ocean, increased stratification and changing which interact with eutrophication-induced hypoxia (oxygen concentration below ~60 to 120 μmol 2 kg-1) and biological activity in shelf regions. • Climate change related longer-term oxygen trends are masked by oxygen variability on a range of different and temporal scales. • The decline in the oceanic oxygen content can affect ocean nutrient cycles and the marine habitat, with detrimental consequences for fisheries, ecosystems and coastal economies. • Oxygen loss is closely related to ocean warming and acidification caused by CO2 increase driven by CO2 as well as biogeochemical consequences related to anthropogenic fertilization of the ocean; hence a effort investigating the different stressors will be most beneficial to understand future ocean changes.