254 WOOSTBR AND REID [ CHAP. 11 



Yoshida (1955) and Yoshida and Mao (1957). The descriptive knowledge of 

 the eastern parts of oceans has been greatly advanced: in the North Pacific by 

 the monthly surveys of the California Cooperative Oceanic Fisheries Investiga- 

 tions (Reid, Roden and Wyllie, 1958), and by cruises of the University of 

 Washington and the Pacific Oceanographic Group of Canada; in the South 

 Pacific by occasional studies off the Peruvian coast (Posner, 1957 ; Wooster and 

 Cromwell, 1958); and in the Atlantic off the South African coast by William 

 Scoresby (Hart and Currie, 1960) and by repeated cruises of the South African 

 Division of Fisheries (e.g., Buys, 1959). 



Although the descriptive data are still fragmentary and the theoretical studies 

 incomplete, it seems desirable to synthesize on a comparative basis what is 

 known about the common features of this important class of ocean currents. 

 Knowledge of the similarities and differences between these analogous pheno- 

 mena may serve to stimulate theoretical investigations and should facilitate 

 the design of more efficient observational programs. 



2. Common Features of Eastern Boundary Currents 



If the eastern boundary currents had nothing more in common than their 

 location, it would be of little interest to discuss them as a group. In fact, how- 

 ever, they all have certain important characteristics which make it profitable 

 to examine them on a comparative basis. These common characteristics pertain 

 to their source waters and surface characteristics, the nature of their flow, and 

 the phenomena resulting from the local atmospheric circulation and the 

 presence of boundaries imposed by the continental land-masses. 



A. Source Waters 



Where the eastern currents are well developed, they are fed by waters 

 carried eastward in the west wind drifts. In the North Pacific, for example, 

 the North American continent is so located as to block completely the west 

 wind drift, a portion of which turns north to feed the Alaskan Current, the 

 remainder turning south into the California Current. In the South Pacific and 

 South Atlantic the continents extend far enough south to intercept at least a 

 part of the flow of the west wind drift, which turns north in the Peru and 

 Benguela Currents, respectively. 



In the Indian Ocean, on the other hand, the west wind drift lies well south 

 of the Australian continent, a fact which may be responsible for the apparent 

 absence of a well-developed eastern boundary current in that ocean (Schott, 

 1933). In the North Atlantic the principal eastern boundary in the subtropical 

 gyre is the northwest coast of Africa along which flows the Canary Current. 

 Farther north the flow into the Norwegian Sea can be considered analogous to 

 the Alaskan Current. 



B. Surface Characteristics 

 Since the eastern boundary currents flow equatorward from relatively high 

 latitudes, it is to be expected that their waters will be at lower temperatures 



