東部深層海水創新研發中心

The heat flux through the ocean floor, about 10−6 cal/cm2 sec, is in agreement with the assumption of an earth of chondritic composition. With the assumption of a U and Th content equal to that of chondrites for the whole earth, a helium production rate of the order of 3 × 10−6cm3 STP/cm2 year can be calculated. The diffusion constant of He increases rapidly with increasing temperature and, therefore, it does not seem impossible that the He, just as perhaps the heat produced by the decay of U and Th, has reached a steady rate of loss from the interior of the earth equal to the rate of production.

Measurements of the C14 activity of the bicarbonate in Pacific Ocean water, by Bien, Rakestraw and Suess (1963), have shown that it takes about 700 years for the deep ocean water to travel from the Weddell Sea, in the Antarctic Ocean, to the North Pacific. If one assumes a chondritic earth that is giving off helium at a rate at which it is produced through radioactive decay, then an increase of about 20 per cent can be expected in the helium concentration of deep-sea water which, according to Königet al. (1964), is about 4 × 10−5 cm2STP/liter. The measurements carried out so far, of He in deep water from the South Indian and from the North Pacific Oceans, indicate an increase of about 6 per cent. Because of various possible sources of error, this value should be considered an upper limit, and further studies are necessary before an absolute value for the magnitude of the flux of He through the ocean floor can be given. Such an absolute value would be interesting in connection with questions concerning the distribution of radioactivity in the interior of the earth and the loss of hydrogen and helium from the top of the atmosphere of the planet. It would be especially interesting in connection with a possible helium gradient below the ocean floor: a possibility to be considered in connection with the planning of deep ocean and Mohole drilling.