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Oceanic oxygen ‘gO2ing’; but where? - ‘Henry’s Law’: is oceanic oxygen buffering atmospheric oxygen loss? - An extinction risk?
  • Robert Brown
Robert Brown
McCarrison Society

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Greater public, and research, focus on oceanic and atmospheric oxygen budgets is needed. Oceans are “losing their breath”; there has been a 1-2% loss, 77-154 gigatons (GT) of total oceanic oxygen (O2) 7,700GT (est.), over the last 50 years. Low O2 ocean areas occur more frequently and more widely; O2 minimum zone (OMZ) depths are rising; and sulphidic events are more common. Where is lost ocean oxygen ‘gO2ing’? Oxygen (O2) is recharged by phototropic O2 producing organisms in both the oceans and on land. Pre-human activity, O2, and CO2 (190-260ppm.) levels likely oscillated within a relatively stable band, for 800,000 years or more. Thus, O2 usage by volcanism, fires, and soil and sea biomes, must have balanced ocean and land based photosynthetic O2 production, as cyclically regulated by ‘Gaian’ feedback. Therefore, additive anthropogenic related increases in CO2 production, must result in net atmospheric O2 loss, including ocean outgassing. Importantly, exchange of oxygen between the oceans and atmosphere is determined by ‘Henry’s Law’, as influenced by oceanic temperature change (warmer waters dissolve less oxygen), and also salinity. Undissolved oxygen concentrations within upper ocean layers, will be higher due to the water pressure gradient, so less oxygen being dissolved at lower pressures. Thus, subject to usage by sea life forms; and thermoclines and haloclines; will likely be replenished from below, tending to surface saturation, even if the OMZs are rising so decreasing in depth? Henry’s law dictates, as anthropogenic reduction of atmospheric O2 reduces partial pressure, dissolved ocean oxygen will equilibrate, releasing stored oxygen to the atmosphere. Thus, over time, if atmospheric O2 continues to fall due to anthropogenic usages, irrespective of other factors, oceanic O2 will arguably be diminished year on year; ultimately will oceans become sufficiently anoxic to be unstable? Research suggests risk of species extinction type events of varying severity strongly correlate to anoxic ocean events. Due to Henry’s Law; will continued anthropogenic oxygen including fossil fuel use, inevitably lead to oceanic oxygen outgassing depletion, and absent change, ultimately an extinction event risk? Is a global Manhattan type project needed to find viable non-carbon-based, non-oxygen using, energy sources?