170 



Thermohaline Features 



WEAKNESSES AND DIFFICULTIES IN THE 

 PRESENT THERMOHALINE HYPOTHESIS 



The chief weakness of the treatment outlined here, as I see it, is the hypo- 

 thetical nature of the quantity pWi. How shall we measure it directly? If 

 frictional stresses in deep water are really negligible, then much information 

 concerning the field of w might be obtained from an analysis of central 

 oceanic hydrographic data, since 



d'^w /? dpv _ ^g dp 



WIND- THERMO - 



DRIVEN HALINE 



(27) 



SUM 



N. ATLANTIC 

 GULF STREAM 



S. ATLANTIC 

 BRAZIL CURRENT 



WATER 



INTERMEDIATE 



DEEP WATER 



ANTARCTIC 

 BOTTOM WATER 



Fig. 8L Schematic diagram of the possible explanation of the very different 

 transport-per-unit-depth curves for the Gulf Stream and the Brazil Current. 



but the available very deep data in the North Atlantic are quite insufficient 

 for such a study. 



Bottom topography must be of considerable importance in the thermo- 

 haline circulation, in which horizontal pressure gradients do not vanish at 

 the bottom. Major topographic features hke the Mid- Atlantic Ridge must 

 be of great importance ; along the eastern rise of this ridge we might very 

 well find a deep southward current (of the boundary-layer type) similar to 

 the one under the Gulf Stream. Where bottom water is confined to deep 

 basins the thermohahne circulation may not be of direct importance, and 

 the circulation within the basin may actually be driven by small frictional 

 stresses exerted upon it by the thermohaline circulation above sill depth, 

 in much the same manner as in an ordinary wind-driven circulation. 



Finally, the vertical distribution of vertical velocity must be of great 

 importance in determining the vertical temperature and salinity structure 



