^IJ^MAGDALENA 



MEXICO 



||4«W. ||2» 110* 108° 106° 



Figure 32. — Horizontal salinity distribution at 50-m. depthfor part of CalCOFI cruise 6004-B and for cruise TO-60-1. 



of the thermosteric anomaly at the sea sur- 

 face. Strong upwelling off Lower California 

 and weak upwelling just north of Mazatlan 

 are evident. The anomaly increases toward 

 Cape Corrientes and the Tres Marias Islands, 

 as does the temperature. A few meters below 

 the surface, however, the anomaly decreases 

 rapidly, as does the temperature {fig. 29). 

 These facts support the view of Roden and 

 Groves (1959) that some upwelling occurs 

 in this area. 



Dynamic height anomaly, AD: geostrophic 

 flow 



Although geostrophic flow can be computed 

 for vertical sections (Montgomery and Stroup, 

 1962), our data made this approach unsatis- 

 factory; vertical profiles seemed to abound 



in currents flowing in opposite directions, 

 alternately, along any given profile. Un- 

 doubtedly this situation was largely due to 

 the slow, meandering currents present. Thus 

 it seemed more sensible to present only hori- 

 zontal distributions of dynamic height anom- 

 alies and associated patterns of geostrophic 

 flow. 



Because most casts on cruise 6004-B went 

 only to a depth of about 600 m. and most of 

 those on TO-60-1 went to about 1,100 m., two 

 kinds of distribution are given below: the 

 dynamic height anomalies over the 1,000- 

 decibar surface (dotted lines) and over the 

 500-decibar surface (solid lines, covering a 

 greater area). Figure 34 provides a graph 

 from which one may read approximate veloci- 

 ties in cm. /sec. or knots (1° of latitude equals 

 60 nautical miles or about 110 km.). 



37 



