Thermohaline Features 



167 



T (l,d) , IO'MViOOM sec 



Sections 3, 4, and 5 are horse-latitude sections where winds are small but 

 the curl of the wind stress is at a maximum. They include parts of the 

 interior that are well removed from the western boundary currents. This is 

 an important region of the ocean from a theoretical point of view. We should 

 estabhsh here whether the interior solution really does correspond to what 

 is expected from the theory of wind-driven currents. It is not an easy 

 section to construct with confidence : no single section is available across the 

 interior of the North Atlantic with many deep-water data (the Dana depth 

 determinations are unrehable). Moreover, 

 two stations such as those used in section 

 3 are really not sufficient below the Mid- 

 Atlantic Ridge : the pressure gradients in 

 the two basins may be different. Section 4 

 is composite. Below 2000 m. it is most 

 unsatisfactory. Section 5 is made from 

 Worthington's rehable new deep-water 

 data, but it does not include the entire 

 width of the North Atlantic. It is com- 

 puted from the bottom. The conservation 

 of mass requires that the reference level 

 be placed at about 1200 m., and it is 

 interesting to note that this depth roughly 

 coincides with the level at which the great 

 salt pall from the Mediterranean seems to 

 hang. From the fact that this highly saUne 

 water extends almost due westward in 

 a tongue issuing from the Straits of 

 Gibraltar it may be shown that at depths 

 of between 1000 and 2000 m. the value 

 of the meridional component of T{z, b) 

 must be less than 0-2 x 10^ m.^/100 m./sec. 

 Were it greater, the wedge of Mediterra- 

 nean Water would not point due west — there would be a perceptible tUt. 

 A choice of about 1600 m. is indicated by the curves in fig. 79. In section 5, 

 for which good deep-water data are available, this does not imply large 

 transports of deep water and bottom water. The total vertically inte- 

 grated transport across section 3 appears to be of the order of 



30-40 X 10« m.3/sec., 



a figure not inconsistent with the interior (central) solution given by the 

 Munk theory. 



Let us now proceed to discuss other sections in fig. 79. The northernmost 



Fig. 80. Detail of the trans- 

 port-per-unit-depth function T(z, 

 d) for the Gulf Stream sections 

 shown in fig. 79. 



