448 



Tides in the Mediterranean and Adjacent Seas 



and travelling towards the Bering Strait. The independent tide is insignificant, 

 because the semi-diurnal tide-generating forces are very small in the vicinity 

 of the pole. One then approaches the presentation given by Fjeldstad of the 

 co-tidal lines, which reproduces the observations correctly. However, the 

 lack of observations precludes an actual tidal picture of the central basin. 

 See Defant (1928, p. 274) and Tenant (1931, p. 879). 



The case is different for the shelf areas, and for its North Siberian section 

 we have the excellent work by Sverdrup (1926) on the observations made prin- 

 cipally during the "Maud" Expedition in 1924-25. The area comprises the 

 largest continental shelf of the earth, extending from Point Barrow (Alaska) 

 to Cape Chelyuskin (Taimyr Peninsula). The co-tidal lines of the entire area 

 are based on the observations of the tides on coastal stations, and on current 

 observations made on a large number of anchor stations of the "Maud". 

 Sverdrup's presentation has been reproduced in Fig. 190, which shows how 

 the tide wave enters this area from the north (see Table 69). We see that 



105° E Gr 120° 135° 150° 165° 180 



ering Seo 



Fig. 190. Co-tidal lines and range at spring tide for the North Siberian Shelf. — , curves 



indicate the depth contours for 25, 50, 75 and 100 m; the roman numbers indicate the time 



of the co-tidal lines and the time of high water at each station (Sverdrup). 



the co-tidal lines have a tendency to be parallel to the bottom contour lines 

 and to run directly towards the coast. The progressive character of the wave 

 becomes thus apparent. Sverdrup draws special attention to the following 

 points, which result from the discussion of the observations: 



(1) The tidal currents are not alternating in the direction of progress of 

 the wave, but throughout the area the currents rotate cum sole (see Table 70). 

 The large and small axes of the current ellipses are about the same for all 



