0828 



0707 



10056 



(a) PLASTIC SAMPLER CAST 4 I _ NOON POSITION: 2I°29'N. 

 (T) PLASTIC SAMPLER CAST 4 2 I 10° 04' W. 



(c)PS,C- AND HYDROCAST 4.3 

 (T) HYDROCAST 4 4 



KILOMETERS 



Figure 36. — Track at front 4 (23 May 1960), showing positions of hydrocasts, plastic 

 sampler casts, and net tows. The track has been broken and separated at 0821 hours. 

 (X) for clarity of presentation. 



21.00° C.) water had mixed with the warm 

 saline water on the warm side of this front. 

 I assume that this upwelled cool, low-salinity 

 water was on the cool side and gradually 

 mixed with the water on the warm side, but 

 at the same time the water on the cool side 

 was being cooled further (19.96° down to 1 9.34° 

 C.) by advection of upwelled water north of it. 

 Thermosteric anomaly, dissolved oxygen, 

 and phosphate content show strong vertical 

 gradients at depths corresponding roughly to 

 the thermocline; the profiles of these prop- 



erties qualitatively resemble that of the temp- 

 erature. 



Like front 2, but in contrast to front 5, 

 there are strong density differences at any 

 given depth down to about 150 m. at front 4, 

 This front, much more than the rest, shows 

 the density discontinuity commonly considered 

 necessary to the existence of a front. 



A plastic sampler cast was made on either 

 side and in the middle of this front, though 

 only three bottles per cast were used, at 

 surface and depths of 25 and 40 m. (table 6). 



48 



