71 



currents flow much like the surface winds do about a barometric 

 anticyclone in the atmosphere, and for the same reasons of gradient 

 gravity pull as modified by earth rotation. The Lows, on the other 

 hand, are actual depressions in the sea surface caused by denser 

 water which is depressed because it is heavier than that surrounding 

 it. Such hollows have counterclockwise currents eddying about 

 them in the northern hemisphere just the same as the barometric 

 cyclones have counterclockwise wind systems about them. In 

 reality the w^ater simply tries to find its own level by slipping down off 

 the Highs and down into the Lows, but it is deflected about 90° by 

 the effect of earth rotation and so spirals around and around them. 



The arrows on the current maps show the computed directions of 

 general flow of the local ocean currents and therefore show the prob- 



JGRAND 



BANKS 





J 



S 



1150 



•^134 



^31.- 



// f 74.70 



5813 



<?30 



SET SEVEN 

 JUNE 6 TO 18. 



^4"N. 



41* W. 



50'WS^^^ 



43'N.- 



48* W. 



Figure 20.— Current tendency diagram 



able paths of any bergs that might be located in the vicinity at the 

 time. The bergs, being but relatively httle influenced by winds and 

 shallow surface drifts, move primarily in accordance w^ith the main 

 gradient circulation of the sea. United States Coast Guard Bulletin 

 14, A Practical Method for Determining Ocean Currents, was used 

 to make the current maps. That pamphlet explains all the principles 

 involved and then gives explicit directions for working the ocean- 

 ographic stations and using the results obtained to make the cur- 

 rent maps. 



Where no four-figure number is given by a station it is because 

 either the depth did not extend down to the 750-decibar level, or if 

 it did, then, due to errors of observations, no reasonable value for the 

 depth of the 750-decibar level below the surface could be computed. 



