winter ocean circulation and the mean sea 

 level pressure distribution in January. A 

 large anticyclonic gyre dominates the ocean 

 circulation (fig. 2a, page 4) over most of 

 the North Pacific between 10° N. and 45° N. 

 latitudes. The middle portion of the gyre 

 contains two distinct centers which lie 

 south of Japan and northeast of Hawaii, re- 

 spectively. The peripheral portions of the 

 gyre include four well-known current sys- 

 tems: the Kuroshio which flows northeast- 

 ward along the southeast coast of Japsm, 

 the North Pacific Drift which traverses the 

 ocean from west to east at mid-latitudes, 

 the California current moving southeastward 

 along the California and Baja California 

 coast and the westward flowing North Equa- 

 torial Current between 10° N. and 20° N. 

 latitudes. Other major circulation features 

 are the Oyashio current which flows south- 

 westward along the east coast of Kamchatka 

 Peninsula and a cyclonic (counter-clockwise) 

 gyre in the Gulf of Alaska. South of the 

 North Equatorial Current, approximately 

 between 5° and 10° N. latitudes, is the 

 eastward flowing Equatorial Countercurrent . 



The principal features of the atmos- 

 pheric sea level pressure field in January 

 (fig. 2b, page 4) are the Aleutian Low, 

 centered over the Aleutian Islands, and the 

 East North Pacific High lying between Hawaii 

 and the North American west coast. The mean 

 winds blow cyclonically (counter-clockwise) 

 around the Low and anticyclonic ally (clock- 

 wise) around the High. 



The mean ocean currents in summer (fig. 

 3a, page 5), although differing in detail, 

 are generally quite similar to those in 

 winter. In sharp contrast, the sea level 

 pressure field in July (fig. 3b, page 5) 

 is markedly different from that in January, 

 with high pressure and anticyclonic winds 

 dominating most of the ocean sirea. Thus, 

 it is evident that seasonal changes in cir- 

 culation patterns are much greater in the 

 atmosphere than in the ocean. 



The location and orientation of the 

 pressure gradients were chosen with reference 

 to the principal branches of the ocean cir- 

 culation. In doing this we hoped to define 



26a 



Figure 4. --Location of points, marked by open circles, used for reading supplementary pressure 

 differences given in tables 3 and 4. Triple Island and location 8 are also shown. 



