current information are seldom available to aid construction of sea tem- 

 perature charts. Experience indicates, however, that meaningful charts 

 can he realized hy employing injection temperatures according to a pre- 

 scribed technique. 



As will be presently more evident, a ninnber of important current 

 systems with numerous tongues are present in the sea along boundary 

 xones of waters of different origin. Because of the limited width and 

 echoplex configuration of these tongues, the waters associated with oce- 

 anic currents are more difficult to delineate than large-scale systems 

 encountered in weather analyses. 



Figure h presents a vertical temperature cross section and surface 

 current data along the 50th meridian. These data and sections for other 

 ocean areas (not shown) form the bases for the analytical approach de- 

 scribed below. Symmetrical undulation of the isotherms indicates four 

 omjor water masses. 



Upon crossing each mass the stirface current changes direction in 

 an orderly manner; that is, the circulation is cyclonic for cold waters 

 and anticyclonic for warm waters. There is also general agreement be- 

 tween the magnitudes of tempera ture__gradients and current velocity. If 

 V is the surface current velocity, K a vertical vector, positive out- 

 wards, and V T is grad T, the relation V= K crossVT holds in principle. 

 This relation, analogous to that which applies for straight air flow, 

 suggests that water bands can be treated as greatly elongated air masses. 



Vertical symmetry manifested by the isotherms in Figure k is typical 

 of temperature cross sections taken over wide areas of the North Atlantic 

 Ocean, and indicates that wave action and meteorological conditions do 

 not disturb deep cxirrent systems which regulate distribution of temper- 

 ature and related physical proi)erties in the sea» 



Temperature structure (including surface temperature) at any given 

 time in the upper layers apparently depends on the origin and history of 

 the masses as indicated by the two northerronost water masses (Figtire k) 

 which lie in practically the same climatic environment. 



The forces expected to be present at various points in interdepend- 

 ent warm and cold current systems are schematically shown in Figure 5j 

 along with an appropriate velocity profile which is placed on the sea 

 stirface for convenience. If air masses were substituted for water bands 

 in this figure, a similar velocity profile would be expected. Elonga- 

 tion of the body of \iniform warm water can be attributed to frictional 

 drag due to high velocities in the northern transition zone. Under 

 these conditions, the potential width of the uniform water, determined 

 by frictional drag from the stronger transition zone, would decrease 

 with increasing slope along the opposite boundary of the warm water. 



Warm waters flowing zonally in the tropics are subjected to long 

 periods of maximum insolation. This results in mixed-layer character- 

 istics which tend to be conserved by convective mixing at higher lati- 

 tudes. Cold waters from higher latitudes, however, undergo short-term 

 k 



