Diffusion of oxygen into still sea water

Bucket experiments were conducted to measure the rate of diffusion of oxygen into sea water, stripped of dissolved oxygen to about 1 mg/l, of "homogeneous" salinity of 26-30⁰/₀₀ and with a "stable" temperature gradient. In five successive tests, the water required about 60 hours, under calm laboratory conditions, to exceed 7 mg/l at all depths in the bucket. Results of these tests indicated input of oxygen to be much more rapid than expected from molecular diffusion of the Fickian type giving a diffusion coefficient of 6 × 10^-3 cm² sec^-1 compared to 2 × 10^-5 cm² sec^-1. It is suggested that evaporation in the thin water layer at the air/water boundary increases the salinity sufficiently to initiate the transfer of oxygen from the atmosphere into sea water by convective movements, even in the presence of a stable temperature gradient and in the absence of turbulence.