It has been known that the route of the Kuroshio is subject to variation, but neither the cause of the variation nor the character of the Kuroshio itself has been fully understood. Previously the author reported the following three facts:
(1) The Kuroshio is a part of the boundary current of the geostrophical current system constituted round the high salinity region in the North Pacific Ocean.
(2) According as the spreading of the high salinity region varies yearly (Table 1), the geo strophical current system is subject to deformation, which results in variations in the route of the Kuroshio.
(3) Variation in the Kuroshio's route brings about changes in the sea conditions in the neighbouring seas of Japan.
As is seen in Text-fig. I, we can recognize in each ocean a high salinity region like the one found in the North Pacific. Then, it may be allowed to suppose that phenomena analogous to (1)-(3) should take place in and around each of these high salinity regions.
The author, therefore, is strongly inclined to believe that a high salinity region works as the acting center of the variations of sea conditons in each ocean, and that oceanographers must pay more attention to these high salinity regions and study the relation between the spreading of these regions and the accompanying variations in sea conditions.
Furthernore, high salinity regions of different oceans differ in the value of salinity (Text-fig. 1). There should be causes for such differences. One of the suspected causes is the sea-weed floating at the surface of the ocean; evaporation from the sea surface is accelerated by the presence of floating seaweeds, resulting in a higher salinity. The author made some experimental observations in the rate of evaporation from the sea water containing sea-weeds in comparison with that from the free sea water. The results are shown in Table 2.