Tides in the Mediterranean and Adjacent Seas 447 



section his chart looks like Harris's, in the western section it shows less crowded 

 co-tidal lines, in accordance with a deep central polar basin, which was as- 

 sumed by Nansen. The crossing of the entire polar basin takes about 12 h, 

 against 18 h assumed by Harris. 



Defant (1924, pp. 153, 177) includes the Arctic Ocean in his first picture 

 of the tides of the Atlantic Ocean, considering the former a bay with one 

 closed end and part of the Atlantic Ocean. The tides of the Arctic Ocean 

 are considered partly as co-osciliating tides with those of the Atlantic Ocean 

 through the opening Greenland-Spitzbergen, and partly as independent 

 tides. Both components are computed following the method of the step-wise 

 integration of the equations of motion. The influence of the rotation of the 

 earth is taken care of through superposition of transverse oscillations. Tn 

 this way one obtains for semi-diurnal tides two positive amphidromies, one 

 with its centre in the vicinity of Spitzbergen, the other one somewhat beyond 

 the Pole. On the whole, the agreement with the observations is not bad. 

 For the diurnal tides, there is an amphidromy south of Spitzbergen, and 

 the largest part of the polar basin is covered by a progressive wave which 

 covers the distance Greenland-Bering Strait in 12 h. 



The small tidal amplitudes at the north coast of Alaska and East Siberia 

 induced Sterneck (1928, p. 81) to abandon his assumption of a single oscillat- 

 ing area in the entire Arctic Basin. He divides this area into a very deep cen- 

 tral basin and a shallow shelf zone. He then assumes that the tides of the 

 central basin are developed independently of the shelf and are composed of 

 the independent and co-oscillating tides. He found that the M 2 tide is es- 

 sentially a co-oscillating tide with an amphidromy rotating to the right with 

 its centre in the vicinity of the pole, whereas the K x tide seems to be almost 

 a pure independent tide, with an amphidromy rotating to the left and with 

 very small amplitudes. The co-tidal lines of the M 2 tide are extended from 

 the central basin into the shelf zone in the form of a progressive wave and 

 brought into agreement with the observations on the coast. He assumes also 

 that this dissipates tidal energy, but the effect of this dissipation upon the 

 main wave in the central basin is not considered. 



Sterneck's conception of a different tidal behaviour for the two separate 

 areas of the Polar Basin is no doubt justified and logical. But his com- 

 putations are not representative of the actual conditions. The energy lost 

 by friction on the shelf is lost for good and is also a loss for the central basin 

 and, therefore, it is not possible for the co-oscillating tide in this basin to be 

 a standing wave. Beside this loss of energy of the principal wave, Sterneck 

 does not consider the fact that the Arctic Ocean is almost constantly and 

 completely covered by a layer of ice and that, the incoming tide wave suffers 

 another important loss of energy by friction against this layer of ice. It is, 

 therefore, to be expected that the co-oscillating tide of the Arctic Ocean will 

 rather appear as a progressive wave coming from the European North Sea 



