The phenomenon of upwelling which is present along many coasts has been discussed from various points of view. A general explanation of the phenomenon has been given by application of Ekman's theory of winddriven currents (Thorade, 1909; McEwen, 1912), and emphasis has been put on the velocity of the vertical motion (McEwen, 1934) or on the depth from which water is brought to the surface (Gunther, 1936; Sverdrup, 1930)....
Sverdrup, H. U.. 1938. "On the process of upwelling." Journal of Marine Research 1, (2). https://elischolar.library.yale.edu/journal_of_marine_research/526