rather than at station 60, and was not nneas- 

 ured elsewhere. Productivity was much higher 

 at station 62 than at stations 56 and 58, but 

 was not nneasured at station 60 or elsewhere. 



Oceanography of the Gulf of California 



(G. I. Roden and G. W. Groves) 



Knowledge of the physical oceanography of 

 this region (fig. 1), summarized originally 

 by Roden (1958), was added to by analysis of 

 data obtained on seven CalCOFI cruises during 

 1956 and 1957. 



The seasonal variation of temperature, sa- 

 linity, and oxygen at the surface and at sub- 

 surface depths was investigated. It was found 

 that the annual temperature range in the 

 surface layers is very large. Surface tem- 

 peratures vary between 14 and 30 C, in the 

 southern part of the region. In contrast to 

 the pronounced seasonal temperature varia- 

 tions, the salinity does not change much from 

 one season to another. In the south it varies 

 between 34.9 and 35.2700 and inthe northbetween 

 35.4 and 35.7%o. Only in isolated bays does 

 the salinity exceed 36*5^0 or fall below 34,5/oo. 

 During the rainy season (July to September) 

 the salinities near the coast are influenced by 

 runoff. With respect to oxygen, the surface 

 waters are almost saturated, deviations of 

 more than 15 percent from the saturation value 

 occurring only rarely. The highest oxygen 

 values occur in spring and are related to bio- 

 logical activities. The stability of the surface 

 layers is very high, owing to the presence 

 of a very well-developed thermocline. In the 

 southern part of the Gulf the thermocline is 

 pronounced throughout the year and in the 

 northern part during the warm season. As a 

 consequence of this the water below the ther- 

 mocline in the southern part of the Gulf is 

 so depleted of oxygen (between 200 and 500m.) 

 that its presence frequently cannot be de- 

 tected by ordinary methods. 



The area around Angel de la Guarda Island 

 is of special interest. It is characterized at 

 the surface by temperatures lower than any- 

 where else in the Gulf; at depths the tem- 

 perature, salinity, and oxygen values are 

 very much higher than observed elsewhere. 

 This peculiar feature is due to two causes: 

 (1) the presence of a deep and isolated trench 

 (below 250 m.) between Angel de la Guarda 

 and Baja California and (2) the intense tidal 

 mixing. 



The circulation in the Gulf is very com- 

 plicated. At the surface there appears to be 

 an outflow of water in winter and spring and 

 an inflow in sumnner and fall. Below the 

 surface, outflow takes place along the west 

 coast and inflow along the east coast. In the 

 northern part of the Gulf there are strong 



tidal currents, occasionally reaching velocities 

 of several knots. In the vicinity of Cabo San 

 Lucas or Cabo Falso intense temperature 

 and salinity gradients are found at the bound- 

 ary between the cold and low salinity Califor- 

 nia Current water and the relatively warm 

 and high salinity Gulf water (cf. fig. 2). 

 A similar but weaker phenonnenon is observed 

 in the vicinity of Cabo Corrientes where the 

 Gulf water meets the water from the eastern 

 tropical Pacific. All of these fronts are rather 

 shallow phenomena and disappear below about 

 150 m. Below that depth the water is rather 

 uniform and essentially the same as in the 

 equatorial Pacific. 



A paper entitled "Recent oceanographic in- 

 vestigations in the Gulf of California" was 

 published in Journal of Marine Research, 

 vol. 18, no. 1, p. 10-35, 1959. 



The work was supported in part (about 50 

 percent) by the California Marine Research 

 Committee. 



Heat and Salt Budget of the California 

 Current System (G. I. Roden) 



The mean monthly variations in the heat 

 and salt content of the upper 200 m. have been 

 investigated for eight ocean areas off Baja 

 California and California. These variations 

 were related to monthly changes in the rates 

 of incoming radiation, energy exchange with 

 the atmosphere, and advection. With particular 

 reference to the STOR program, we wanted 

 to know whether advection of warm water 

 occurs at any time of the year off the coast 

 of southern Baja California, since this might 

 facilitate the entry of tropical tuna from the 

 south. The following results were obtained: 



1. Significant northward flow off southern 

 Baja California occurs only in late summer 

 (September). 



2. The rate of net incoming radiation off 

 Baja California varies between about 200 cal. 

 cm."^ day"^ in January and about 400 cal. 

 cm."'^ day' in July. 



3. The rate of turbulent energy exchange 

 with the atmosphere off Baja California varies 

 between -70 cal. cm."^ day'' in summer and 

 -140 cal. cm. -2 day-1 in winter. 



4. The rate of heat advection by currents 

 off Baja California varies between -200 to 

 -400 cal. cm. -2 day"^ in winter and spring 

 to about -80 to +200 cal. cm.'^ day'l in late 

 summer. 



5. The rate of advection of salt off Baja 

 California indicates that water of relatively 

 high salinity enters the region between May 



23 



