Solubility of selected gases in the oceans

Compare and explain the solubility of selected gases at increasing depths in the oceans

  • As ocean depth decreases, temperature falls and pressure increases.
  • Thus, the solubility of gases is much greater at greater depths.
  • However, when ocean water is very deep, there is not much mixing of surface water with bottom water, and concentrations are unlikely to reach equilibrium values.
  • For oxygen and carbon dioxide, concentration is also affected by:
    • Rates of photosynthesis, which is confined to where light can penetrate.
    • Rates of respiration and decomposition, which increase with depth.
    • Formation and dissolution of calcium carbonate by marine organisms and local acidic environments respectively.
  • The net result for oxygen is that concentration decreases with depth, reaching a minimum at 500 to 800 metres, then increases lightly due to the inflow of cold, oxygen-rich currents.
  • The net result for carbon dioxide is that concentration increases with depth.