DEPTH OF ZERO INORGANIC PHOSPHATE 



3tf 



N. 



2 8 



26" 



24" 



2 2 



20' 



16' 



Figure 44. — The thickness of the surface waters of the Gulf of Mexico, February and March 

 1962, in which inorganic phosphatewas "zero. "Water entering through the Yucatan channel 

 had no PO^-P (//g. at. /I.) from the surface to a depth greater than 100 m. Only around 

 the periphery of the Gulf was there measurable PO.^-P in the top 50 m. of the water 

 column. 



EXTREME MODIFICATIONS OF 

 GULF WATERS 



Hurricame Betsy entered the Gulf of Mexico 

 on September 8, 1965, after crossing the 

 southern tip of Florida. The storm followed 

 a northwesterly path and crossed the coast 

 to the west of New Orleans, La., in the late 

 hours of September 9. Hurricane-velocity 

 winds extended 130 km. from the center and 

 wind speeds of 190 km./hr. were measured 

 near the "eye." The average forward speed 

 of the storm as it crossed the Gulf of Mexico 

 was 24 km./hr. 



The R /V Al aminos , Texas A&M University, 

 cruised along the edge of the Continental 

 Shelf and occupied a series of bathythermo- 

 graph stations on August 23-24, 1965. Imme- 

 diately following the storm on September 12-13, 

 the Alaminos again cruised the same track. 

 Ten days later, September 20-22, the Bureau 



of Commercial Fisheries M/V Gus III occu- 

 pied stations made earlier by the Alaminos 

 (fig. 45). From the data collected on these 

 cruises, analyses can be made of the water 

 structure before amd immediately after the 

 hurricane, and an insight gained of the rate 

 at which waters affected by a violent 

 storm may return to normal, seasonal con- 

 ditions. 



In August, the waters near the Mississippi 

 Delta had a surface brackish layer spread 

 over waters of normal salinity. The top 

 of the thermocline was bounded by the 28° C. 

 and 29° C. isotherms and began at depths 

 of 20 to 30 m. The thermocline was nearly 

 horizontal in an east-west direction, and 

 the net water motion was parallel to the 

 coast (fig. 46). 



The temperature structure shortly after 

 the passing of Hurricame Betsy was con- 

 siderably different from that in August. The 



39 



