TEMPERATURE (°C 1 / 



2p00 



3,000 



3,500 



Figure 23.~Temperature cross sec- 

 tion from cruise 16, R/V Geronimo , 

 in the Gulf of Mexico, August to Oc- 

 tober 1967, based on potential tem- 

 perature for <6°C. (40° F.). 



hydrographic cruises of the R/V Geromrru) were 

 so large that our principal concern hasbeento 

 analyze this information and to formulate plans 

 and basic questions that should be answered 

 for future operations. The R/V Geronimo 

 cruise data, supplemented by data from other 

 hydrographic operations in the Gulf, permit us 

 to detail the general features and conditions 

 that prevail in the waters of the Gulf and, to 

 some degree, the variations that occur with 



time. . . ^ 



The data from these cruises were put into 

 the computers of the NASA Mississippi Test 

 Facility. Bay St. Louis, Miss., to produce 

 station profiles of temperature, salinity, po- 

 tential temperature, and density {c ^) , J:° 

 compute factors for dynamic analysis of the 

 water circulation. This information is now 

 used for quality analysis of the data and 

 worked up into cross sections (figs, i-i, -^4, 



and 25). , , , , 



A technique for determining the level of no 

 motion for geostrophic current computations 

 was developed and is now being tested. The 

 concept is to examine the relative divergence 

 by comparing temperature profiles for two 

 adjacent stations. Figure 25 is an example of 

 the geostrophic velocities computed by this 

 technique. Because that portion of the Gulf to 

 the west of this section is totally enclosed by 

 land, the net volume transport through the 

 section should be zero. The gross volume 



transport was computed as 43 million m. /sec, 

 the net transport was 0.31 million m.Vsec. or 

 about only 0.7 percent in error. The usual 

 method for computing geostrophic currents is 

 to assume that the level of no motion lies at 

 the deepest level of observation. If such a 

 method were used for the data in figures 23, 

 24 and 25, the pronounced deep currents 

 (maximum value of 6.9 cm./sec. between sta- 

 tions 57 and 58) could not be detected. In this 

 particular section, more than half the volume 

 transport is effected in the waters below 

 1,000 m. (3,300 ft.). 



We have learned from the data collected 

 during the R/V Geronimo cruises that the 

 regions of the Yucatan Strait and the central 

 Gulf are of main importance to the oceanogra- 

 phy of the Gulf. A major leg of the Gulf Stream 

 system enters the Gulf through the Yucatan 

 Strait. This flow produces a strong looping 

 current in the eastern Gulf, and the exchange 

 of water in the central Gulf between this loop 

 current and the western Gulf apparently de- 

 termines the conditions that prevail m the 

 waters of the western Gulf. For future opera- 

 tions, therefore, primary interest should be 

 given to the waters of the Yucatan Strait and 

 the central Gulf, particularly off the shelf break 

 along the northern edge of the Campeche Shelf 

 of the Yucatan Peninsula. 



During cruise 3 of the r/V Oregon 11 

 (October 8-18), we completed 14 of the intended 



34 



