and 18 slope gradually downward, and the surface values of 36.77 /00 at 

 station 7 can be found at a depth of 140 meters at station 18. 



D. DENSITY 



1. Surface - The horizontal distribution of surface density shows 

 highest values in the southern portion of the Tongue. Density values 

 (expressed as sigma - t) increase from 24.78 along the northern transect 

 to 25.09 at the southernmost station. In general, the highest density 

 values are found along the western portion of the basin and minimum 

 density values are found along the eastern portion of the basin. An 

 example of this horizontal change can be found by comparing the values 

 along the midtransect. In this example, density values range from 

 24.95 at station 10 to 24.85 at station 12. A similar change can be 

 noted at the northern transect, although the magnitude is less marked 

 than over the central portion. 



2. Vertical Cross Sections 



a. The vertical distribution of density along the southern 

 transect demonstrates that the waters in this region are nearly isopycnal 

 (Fig. 20). At station 3, isopycnal conditions can be found to depths of 

 about 40 meters, whereas, at station 4 they can be found to depths of 20 

 meters. This condition also exists at station 5. At station 6, unstable 

 conditions, probably arising from the intrusion of high saline water off 

 the shoal banks, creates a density inversion in which density values 

 increase from 24.87 to 25.00. The pycnocline commences at approximately 

 150 meters at stations 3 through 5 and approximately 170 meters at 

 station 6. For the most part, isopycnals along this transect are nearly 

 horizontal, except between stations 5 and 6 where a horizontal gradient 

 exists causing the isopycnals to slope gradually downward. 



b. Stations 10 through 12 - No evidence of density inversions 

 can be found along this transect (Fig. 21). Nearly isopycnal conditions 

 prevail from the surface to depths of approximately 50 meters, with a 

 gradual increase below this depth. The pycnocline begins at depths of 

 approximately 160 meters and the isopycnals are nearly horizontal across 

 the entire transect. 



c. Along the northern transect, isopycnal conditions prevail 

 from the surface to 90 meters at station 15, decreasing eastward to 

 approximately 40 meters at station 18 (Fig. 22). As in the central 

 transect, a gradual increase in density can be found between this level 

 and the main pycnocline which can be found at approximately 150 meters 

 at all stations. 



3. Longitudinal Cross Section - The longitudinal variation in density 

 is shown in Figure 23. The most striking feature of this figure is the 

 orientation of the main pycnocline, which for the most part is nearly 

 horizontal below depths of 150 meters. Above this level, the density 



10 



