HYDROGRAPHY OF THE MARINE WATERS 17 



Figure 4 also shows the current produced there by the average winds from 

 the eight major directions. These prove to be a much greater force than the 

 tides at the coastal lightship stations. Of course these wind currents are 

 extremely variable, as is evident from Table 6, in which the number of 

 observations at a given wind direction and velocity indicates the propor- 

 tionate number of times each wind prevailed.^ From this tabulation the 

 approximate frequency of a characteristic current effect is evident and, when 

 the information in Table 6 is supplemented by that in Figure 26, frequencies 

 for specific months can be estimated. The decreasing of the wind currents 

 from the Diamond Shoal to the Cape Lookout to the Frying Pan Shoals 

 Lightship correlates with the location of these stations, the lightship farthest 

 offshore showing the greatest current, and so on. Also, all three of these show 

 stronger wind currents than other lightships along the eastern coast of the 

 United States. 



In oceanic waters of limitless depth, Corioli's force directs a surface current 

 45 degrees to the right of the wind's path (this increases with depth; so 

 the deeper currents may literally flow against the wind). The Corioli's effect 

 is greatly minimized over the continental shelf, however, because the water is 

 comparatively shallow. In addition the shoreline and bottom configurations 

 have effects on wind currents to the extent that some are actually guided to 

 the left instead of the right (Table 6). 



The little that is known regarding the flow from the sounds and rivers has 

 been discussed in the section on Circulation in the Sounds and will be men- 

 tioned further in the section on Salinity and Nutrient Salts. All that can be 

 added is that this flow simply augments the ebb of the tide through inlets, 

 etc., that it may have pronounced local influence but little gross effect on 

 currents, and that its effect will tend to be deflected to the south and southeast 

 by Corioli's force. 



The effect of the Gulf Stream System on these coastal waters remains 

 questionable. A widely accepted theory proposed by Abbe (1895) relates the 

 peculiar cuspate shoreline of North Carolina to hypothetical counterclock- 

 wise back eddies of the Florida Current (Figure 5 ) . Supporting this hypothesis 

 are the south and southwestward migration of inlets and shore prominences 

 (see section below on the Offshore Bar and Its Inlets) and MacCarthy's 

 (1931) interpretation of the currents as indicated by the distribution of sand 

 grain sizes. Rude (1922) has opposed Abbe's theory, however, on the grounds 

 that his observations in the area show currents setting approximately with 

 the wind, that the winds blow from southerly directions about as often as 

 from northerly, and that since storm winds are chiefly from the north and 

 northeast, the stronger currents resulting from these occasional high winds 



8. The wind velocities for such observations were determined subjectively by the observers, 

 which greatly limits their accuracy. 



