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Ocean deoxygenation is the reduction of the oxygen content in different parts of the ocean due to human activities. [ 2 ] [ 3 ] There are two areas where this occurs. Firstly, it occurs in coastal zones where eutrophication has driven some quite rapid (in a few decades) declines in oxygen to very low levels. [ 2 ]
A new study uncovers aquatic deoxygenation as Earth's 10th tipping point, threatening ecosystems and humanity's future. ... ozone depletion, ocean acidification, freshwater change, and more. (Of ...
Open ocean areas with no oxygen have grown more than 1.7 million square miles in the last 50 years, and coastal waters have seen a tenfold increase in low-oxygen areas in the same time. [34] Measurement of dissolved oxygen in coastal and open ocean waters for the past 50 years has revealed a marked decline in oxygen content.
Ocean deoxygenation is an additional stressor on marine life. Ocean deoxygenation is the expansion of oxygen minimum zones in the oceans as a consequence of burning fossil fuels. The change has been fairly rapid and poses a threat to fish and other types of marine life, as well as to people who depend on marine life for nutrition or livelihood.
In OMZs oxygen concentration drops to levels <10 nM at the base of the oxycline and can remain anoxic for over 700 m depth. [7] This lack of oxygen can be reinforced or increased due to physical processes changing oxygen supply such as eddy-driven advection, [7] sluggish ventilation, [8] increases in ocean stratification, and increases in ocean temperature which reduces oxygen solubility.
Ocean deoxygenation – Reduction of the oxygen content of the oceans; Oxygen minimum zone – Zone in which oxygen saturation in seawater in the ocean is at its lowest; Shutdown of thermohaline circulation – System of surface and deep currents in the Atlantic Ocean
Global map of low and declining oxygen levels in the open ocean and coastal waters, 2009. [1] The map indicates coastal sites where anthropogenic nutrients have exacerbated or caused oxygen declines to <2 mg/L (<63 μmol/L) (red dots), as well as ocean oxygen minimum zones at 300 m (blue shaded regions).
These low oxygen ocean areas are expanding as a result of ocean warming which both reduces water circulation and also reduces the oxygen content of that water, while the solubility of oxygen declines as the temperature rises. [56] Overall ocean oxygen concentrations are estimated to have declined 2% over 50 years from the 1960s. [56]