164 Thermohaline Features 



there is a finite interval of no horizontal divergence, this is a level of no 

 motion. 



By applying these expressions to the central regions of the oceans, and 

 using the principle of mass conservation, expressions are obtained for the 

 integrated wind-produced and thermohaHne-produced transports in the 

 western boundary currents. (It is not necessary to consider the detailed 

 structure of these currents, be they viscous or inertial.) A schematic model 

 of a rectangular basin is examined, and an attempt is made to relate the 

 theory in a more schematic form to actual measurements in the Atlantic 

 Ocean. Several predictions (or more properly, deductions) are made: for 

 example, that there is a great thermohaline countercurrent under the Gulf 

 Stream. It is intended that these predictions shall stimulate direct measure- 

 ments of deep ocean currents. The well-known discrepancy between the 

 transports of the Gulf Stream and Kuroshio computed from the wind theory 

 (Munk, 1950) and those determined from observation (dynamic computa- 

 tion) is resolved. It is important to note that the Equatorial Current trans- 

 ports in the theories of Sverdrup (1947) and Reid (19486) do not exhibit this 

 discrepancy. Finally, some of the limitations and perplexities of the 

 rectangular model are discussed. 



THE VORTICITY EQUATION FOR THE CENTRAL 

 OCEAN, WIND STRESS ONLY 



The physical meaning of the 'curl' equation in the theory of the wind- 

 driven oceanic circulation, as first propounded by Sverdrup (1947) and 

 further developed by Munk (1950), can be most easily appreciated when 

 explained in the following way. We write the linearized stationary equations 

 of motion in the form 



dp dr^ 



(1) 



Horizontal viscous stresses, inertial terms, and time dependence are neg- 

 lected. The a:-axis is positive toward the east, the ^/-axis is positive toward 

 the north, and the 2-axis is positive upward. The velocity components u 

 and V, the density p, the hydrostatic pressure jp, and the vertical shearing- 

 stress components Tj. and Ty are regarded as functions of x, y, and z. The 

 Coriohs parameter /is regarded as a function oiy alone. 



The equations (1) are now integrated from the surface z = ZQto some great 

 constant depth 2= — ^, at which one supposes that the horizontal pressure 



