Section outline

    • Where oxygen exists on Earth and how much it moves Page

      　I explained that climate change is "the history of the carbon cycle." In contrast, the evolution of life can be described as the "history of oxygen circulation." Generally, the ``earth's oxygen cycle'' does not attract attention, but it is more fun to think about it in conjunction with the carbon cycle. Let me introduce some findings about Earth's oxygen in comparison to carbon.

      　The major difference between oxygen and carbon is their abundance on Earth. Among the elements that make up the earth, oxygen (30%) is second only to iron (32%). Most oxygen exists in the Earth's crust and mantle as SiO2 and MgO (Morgan, PNAS, 1980). By the way, most of the iron exists in the core, and also exists as iron oxide in the crust and mantle.



      The original figure was created using data from Garrels, et al., Controls of Atmospheric O2 and CO2: Past, Present, and Future, American Scientist, 64, 306-315 (1976). Regarding the amount of oxygen on Earth, this data is taken from an earth and planetary science textbook. The amount of oxygen in seawater was calculated assuming the average oxygen concentration of seawater as 0.2 mmol/kg.



    • 【Basics of the concept of oxygen in oceanography】


      ・The existing amount of free oxygen (O2) on Earth is overwhelmingly greater in the atmosphere than in the ocean.

      →　Most of the oxygen in seawater comes from the atmosphere.

      ・There is 15,200 times more oxygen (O2) in the atmosphere and ocean than is used by living things in a year.

      →　However, seawater naturally has low levels of O2, so if it is isolated from the O2 supply from the atmosphere at depths below the surface, the effects of O2 supply and consumption by marine organisms will be clearly visible.




      With this in mind, please learn about ocean oxygen.