A meridional section of oxygen concentration for the Pacific Ocean along the date line. The lower figure is an enlargement of the upper 1500 m of the same section.

Note the decrease of oxygen concentration with depth. At the surface, oxygen concentration is above 7 ml/l in the polar regions and closer to 4.5 ml/l in the tropics. Below about 1000 m the concentration falls off to levels near 4 ml/l. The North Pacific Ocean is particularly low in oxygen at depth, with oxygen concentrations below 2 ml/l. Such extreme values are not typical for all deep ocean basins. The low oxygen concentratrations at depth are mostly due to oxygen uptake as nutrients are brought back into solution (remineralised); oxygen uptake by marine life is only of very minor importance.

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