scale such a general assumption may be 

 justified, but in the relatively confined and 

 complex Subarctic region, some doubt exists 

 as to the validity of geostrophic currents. 

 However, since the level of no motion is not 

 known and direct current measurements were 

 not made, the geostrophic calculations are the 

 only method available to show flow, and are 

 presented with the previously stated reserva- 

 tions. 



Profiles of isobaric surfaces relative to 

 the 1,000-decibar surface are shown in figure 5 

 and the vertical profiles of geostrophic cur- 

 rents are shown in figure 6. 



At long. 1750 W. (fig. 6a) the Alaskan 

 Stream was evident south of the Aleutian 

 Islands to lat. 50° N. and attained a maximum 

 velocity of about 10 cm. /sec. near the Islands. 

 South of lat. 50° N. the current structure was 

 complex with marked frontal zones at latitudes 

 48° and 46° N. Between lat. 46° and 42° N., 

 there was a pronounced eastward flow reaching 

 8 cm. /sec. near latitude 44° N. 



At long. 155° W. (fig. 6b) the axis of the 

 westward flowing Alaskan Stream occurred 

 offshore at lat. 54° N. with a speed in excess 

 of 20 cm. /sec, near the surface, and speeds 

 in excess of 6 cm. /sec. were present below 

 600 meters. The westward flow extended to 

 lat. 52° N., south of which the predominant 

 flow was eastward (except for an insignificant 

 westward flow of approximately 0.3 cm. /sec. 

 between lat. 50° and 51° N.) with the main 

 axis near lat. 48° N. 



Geostrophic currents along lat. 47° N. 

 (fig. 6a) were weak and variable. Velocities 

 in excess of 2 cm./sec. were found only off 

 the Washington coast, and this northward flow 

 is substantiated by recoveries of drift bottles 

 released during the cruise near the coast and 

 reported coming ashore all along the west 

 coast of Vancouver Island. 



Temperature 



One of the purposes of the winter cruise 

 was to observe conditions during the period 

 of maximum cooling of the surface layer 

 which was known to occur during the period 



January to March. At most stations along 

 long. 175° and 155° W. the temperatures at 

 100 meters were equivalent to those at the 

 surface and in some instances the surface 

 temperatures were lower, which indicates that 

 no appreciable spring warming had occurred. 



There are three significant features in the 

 temperature profile along long. 175° W. (fig. 

 7a): First, the temperature maximum at 125 

 to 200 meters between Adak Island and lat. 

 50° N. which is associated with the westward 

 flowing Alaskan Stream. Winter cooling had 

 not penetrated deep enough into the water 

 column to remove evidence of this stratum. 

 It is apparent that when complete vertical 

 mixing occurred, as at lat. 49°30' N., it is 

 difficult to distinguish the origin of this water. 



Second, the presence of a temperature- 

 minimum between lat. 48° to 46° N. at 150 

 meters indicates the stratum to be an intrusion 

 of cold water from the Oyashio region rather 

 than a consequence of local cooling. The frontal 

 zone which occurred between lat. 50° to480N. 

 separates these two flows. 



The third feature is the sharp downward 

 slope of the 4° C. isotherm at lat. 45° N., 

 (indicated in figure 2 as denoting the Polar 

 Front) south of which the heat content of the 

 water column is greatly increased. 



These three features are also evident in the 

 profile along long. 155° W. (fig. 7b). South of 

 the narrow band of cold water near the con- 

 tinental slope the temperature -maximum asso- 

 ciated with the westward flowing Alaskan 

 Stream extends from approximately lat. 55°30' 

 to 52°30' N. Compared with the conditions at 

 long. 175° W. the Stream at long. 155° W. was 

 about twice as wide; the maximum temperature 

 was about 1° C. higher; and, as indicated in the 

 section on geostrophic currents, the maximum 

 velocity was almost twice as great. 



The temperature -minimum stratum (reflect- 

 ing the intrusion of water from the west) was 

 displaced northward and occurred between 

 lat. 48° and 51° N. The minimum temperature 

 had increased 0.3° C. and the stratum had 

 spread laterally. South of lat. 48° N., the 

 downward slope of the 4°C. isotherm, although 

 present, was not as sharp as at long. 175° W. 



