From Henry's Law, it can be deduced that, in the balance between ocean and atmosphere, the concentration of a gas dissolved in water is directly proportional to its partial pressure in the atmosphere, although the solubility of a gas in sea water can vary depending on specific parameters.

Since the advent of photosynthesizing organisms still in the Archean, one must assume, after the equilibrium of the redox conditions of the atmosphere, an increasing supply of oxygen in the hydrosphere-atmosphere system.

Thanks Pedro. The NOE does not appear to be as clear cut as the Paleoproterozoic Great Oxygenation Event (GOE).

The timing and magnitude of the NOE remains poorly determined (Lyons et al., 2014; Och and Shields-Zhou, 2012), along with its alleged unidirectional increase and supposed causal relationship to evolution of early animal life (Sahoo et al. 2016).

A dynamic environment with cycles of both oxidation and reduction occurring is suggested for the Neoproterozoic. Uranium isotope evidence for Cryogenian global marine oxygenation and return to anoxic conditions suggests that Neoproterozoic oxygenation was not an irreversible, stepwise increase in oxygenation; at least one major interval of oxygenation following deposition of Sturtian strata was followed by a return to widespread anoxia prior to deposition of Marinoan strata. (Laue et al. 2017). Similarly cerium depletion studies (Wallace et al. 2017) suggest there was a protracted and irregular oxygenation increase that extended well into Phanerozoic strata. Integrated data for sulfur isotope patterns in pyrite, iron speciation analysis, and redox-sensitive elements from euxinic shales of a deep-water slope section in the Yangtze platform, South China, indicate multiple oxygenation events in overall anoxic Ediacaran strata (Sahoo et al. 2016).

The increase in oxidized species in the Neoproterozoic stratigraphic record may indicate the movement of elements in a reduced state (such as S-2, Fe2+, and CH4), from deeper water to above wave base and to the surface where they underwent oxidation by atmospheric oxygen.

Precambrian-Cambrian transition phosphorite is associated with a worldwide marine transgression, and catastrophic ocean water mixing (deep anoxic and shallow oxic oceanic waters) as inferred from sulphur isotopes (Cook 1992). Upwelling of hydrogen sulphide-rich deep ocean water to become surface waters at the Precambrian-Cambrian transition is indicated by the basal Cambrian black shale molybdenum isotope signal (Wille et al. 2008).