24< 

 N. 



22' 



20' 



MEXICO 



MAZ ATLAN 



360- 



II4°W. 



110° 



108° 



106° 



Figure 33, — Horizontal distribution of thermosteric anomaly at the sea surface for part of CalCOFI cruise 6004-B and for 



cruise TO-60-1. The contour interval is 25 cl./metric ton. 



Figure 35 shows the distributions of the 

 anomaly at the sea surface; arrows indicate 

 the direction of geostrophic flow. The frontal 

 system and the California Current water 

 entering the Gulf entrance show clearly (re- 

 gardless of whether the 500- or the 1,000- 

 decibar reference surface is used). As might 

 be expected from the temperature distribution, 

 flow in the upwelling region off western Lower 

 California is southward, because the tem- 

 perature decreases toward the coast. 



This picture is essentially unchanged in 

 the upper 100 m., though the flow in general, 

 and in the frontal system in particular, is 

 somewhat weaker. At 125 m. there is a more 

 definite indication of a flow into the Gulf in 

 the southeastern part (fig. 36; note smaller 

 contour interval). In contrast, the flow off 



Lower California has become less directed 

 and weaker. 



The most persistent feature is the distribu- 

 tion immediately about Cape San Lucas. The 

 isopleths seem to run parallel to the coast 

 of the peninsula. This characteristic is found 

 at least to 200 m. Probably the outflow from 

 the Gulf is contained at the Cape by the winds 

 which blow mainly from the northwest in the 

 spring and in much of the rest of the year, 

 except in autumn (Meteorological Office, 

 London, 1956). I found in front studies (Grif- 

 fiths, 1965) that the mountainous land acts 

 as a windbreak which probably prevents the 

 removal of water by wind action from the lee 

 of the Cape. Thus the frontal system tends 

 to be preserved better near the Cape than it 

 is out to sea. 



38 



