region. As can be seen in the figure, current measurements are highly diverse and vary from 

 rather high surface speeds, 25 to 1 20 cm/sec, in the northern portion near the coast (profile 

 8-1 1) to the very low speed currents, less than 10 cm/sec, at 35°N (profile 14). The north- 

 ern area (48° to 52°N) is the terminus of the Aleutian Current and the southeastern portion 

 of the northward-moving Alaska Current. In locations 8 and 9 the current remains near the 

 same velocity or increases with depth; there may be some tidal influence from the inlet 

 north of Vancouver Island. Slightly further south the strong surface currents (greater than 

 1 m/sec in locations 10 and 1 1) are reduced to nearly 25 cm/sec by 25-meter depths. It is 

 probable that these rather high maximum surface current speeds were wind-induced (wind 

 velocities are not given). The measurement locations off the continental slope (locations 12, 

 13, and 14) are relatively low (10 to 20 cm/sec) in current speed and nearly constant with 

 depth. In the southern portion of the California Current region the profiles show slow (5 to 

 15 cm/sec) surface currents that decrease in speed slowly with depth or remain roughly 

 constant. 



The need for further current tune histories and depth profiles is apparent. Prior to 

 placement of the prototype marine farm, current velocity profile measurements should be 

 made to estimate better the probable stresses on the substrate and upwelling systems. 



In the central portion of the survey area, northeast of Hawaii, a large gyre is formed 

 during the summer from the forces of the weak easterly-moving North Pacific Current, the 

 southerly California Current, and the relatively strong westerly-setting North Equatorial 

 Current (25 to 50 cm/sec, 13° to 18°N). The current flow in the central gyre area is rela- 

 tively slow, (5 to 15 cm/sec). The gyre tends to disappear in the winter (Fig. 4). Further to 

 the south, the North Equatorial Countercurrent runs steadily towards the east at 25 to 50 

 cm/sec from about 5° to 7°N. At the point of the northward deflection of the countercur- 

 rent as it impinges on the coast of Central America, there is a redistribution of mass that is 

 effected by divergence and crosscurrent flow thus causing an upwelling zone about 400 

 kilometers across (Refs. 24 and 25). This zone is termed the Costa Rica Dome and is char- 

 acterized by lower near-surface temperatures and elevated nutrient concentrations (see 

 Fig. 1). 



From approximately 4°N to TS the high-velocity South Equatorial Current sets in a 

 westerly direction with speeds up to 1 m/sec near the equator. The South Equatorial Cur- 

 rent originates principally from the Peru Current, which moves up the coast of South Ameri- 

 ca with a mean velocity of approximately 30 cm/sec in the region of 10°S increasing to 

 about 45 cm/sec in ^he northern portion where it turns west (regions 9 and 10, Fig. 8) at 

 about 3°S. The surface current velocity is roughly constant both seasonally and over most 

 of its length. Slight seasonal changes are shown in Fig. 8. The current close inshore is under 

 the nearly continuous influence of small-scale upwelling (Ref. 28). The upwelling takes 

 place from about 130 meters from 35°S to 2°S (Ref. 29) and causes lower temperatures and 

 increased nutrient concentrations near the coast. 



Temperature 



Temperature is important biologically for two principal reasons: (1) it has a stimula- 

 tory effect on the growth rate of Macrocystis as the temperature increases from low values, 



15 



