Tides and Tidal Currents in the Proximity of Land 

 Table 38. Tidal currents in the Kattegat, August 1931 



337 



methods, in the current observations made on the light ships Varne, Smith's 

 Knoll, Horn's Reef, etc. The results are in a generally good agreement with 

 those given above. For further investigations on the effects of friction on 

 the tides see also p. 326. 



3. Tides in Adjacent Seas 



In the preceding paragraph we discussed mainly the relations between the 

 vertical tide and the pertaining tidal currents in their vertical distribution. 

 In the following paragraphs we will examine the tides in adjacent seas, which 

 are enclosed seas and communicate with the open ocean only by means of 

 openings. It will facilitate the discussion to treat first the case of a rectangular 

 ocean basin neglecting the earth's rotation and friction (see Defant 1919, 

 1925). The influence of complicated shore and bottom configurations, as 

 well as the Coriolis force and the friction will be discussed next. 

 (a) Independent and Co-oscillating Tide 



If we consider a water mass of which the greatest part is enclosed, we find 

 that the tides occurring herein are of a twofold origin. The tide-generating 

 forces cause periodical horizontal water displacements which produce the 

 independent tides. On the other hand, the tides of the open ocean in front 

 of the opening cause the partly enclosed water masses of the adjacent sea 

 to co-oscillate with the same period as the tides in front of the opening. 

 As the latter is originated by the tide generating forces, these co-oscillating 

 tides have also the periods of the generating force. 



(a) Rectangular basin of the length / with a depth h; closed end is at 

 y = x/l = 0, opening into the ocean is at y = x/l = 1 . It is necessary to 

 add on the right-hand side of the equation of motion (VI. 5 and 8) a periodic 

 force X = w cos (erf -fe) which causes an independent tide, for which the 

 boundary conditions are to be fulfilled: at the closed end £ = 0, at the opening 



22 



