Figure 9. --Distribution of surface isotherms (contour interval: 0.5° C.) at fronts, off Cape San Lucas, Lower California, 

 from the initial thermograph survey (0956 hours 19 April till 1235 hours 20 April 1961), the track of vifhich is shown, 

 -o- time check; -•- temperature check; speculative contour. 



There is some ground, then, for saying that 

 the Cape San Lucas front (3, 5) is, at least in 

 the months of March, April, and May, a fairly 

 stable feature, and that it is oriented roughly 

 parallel to the coast. All subsequent discus- 

 sion in this section on fronts 3 and 5 refers 

 entirely to front 5. 



Surface currents . --As noted above, warm 

 water was transported westward inshore and 

 cool water was transported eastward further 

 offshore. This transport was measured directly 

 by drogues and less directly by GEK. It was 

 also indicated by the ship which practically 

 always drifted along an isotherm when hove to. 



Figure 12 shows. the apparent tracks of the 

 four drogues released at front 5. The dif- 

 ferences in the depths of the parachutes (5 m. 

 and 50 m.) had no apparent effect on the flow 

 pattern. The drogues were all, more or less, 

 carried first northward then westward. Be- 

 cause they were all put in in the middle or 

 slightly toward the warm side of the front, 

 their apparent track is roughly as expected: 

 northward round the end of the cool 'loop', 



then westward to Cape San Lucas. The drogues' 

 paths agree roughly with the flow expected 

 from the surface temperature distribution 

 (assuming it reflects the density difference at 

 depth): looking down the temperature gradient 

 the geostrophic flow is to the right (westward 

 mostly). Their average velocities were, read- 

 ing from north to south in respect of starting 

 positions, 11, 10, 13, and 15 cm, sec."l, 

 slightly less than the average velocity based 

 on GEK measurements (16 cm. sec."l). 



According to GEK measurements, surface 

 currents were somewhat across the isotherms 

 (fig. 13). Two of the values were obtained in 

 the cool water near the eastern end of the 'loop' 

 in the front, indicating the easterly flow of the 

 cool water. The remainder clearly indicated a 

 flow of warm water from the Gulf. The GEK 

 observations were a little northeast of the 

 drogue paths. They showed a south-westerly 

 surface flow in that area. Further west this 

 outflow from the Gulf became westerly, ac- 

 cording to the drogues. However, quite apart 

 from the effects of the difference in location, 

 there may be a difference between a drogue 



16 



