There were 2, 022 such determinations made. Hourly wind observations, 137 observations 

 of pressure of ice, 6 daily, 12 twice-daily and 30 serial oceanographic observations, as well as 

 numerous instrumental observations of current, enabled them to throw light on the dynamics of the 

 drift of ice with great thoroughness. 



Storozhev notes that all the observations of the icebreaker Lenin show that the drift of ice 

 due to tidal currents in the Laptev Sea is 4 to 6 hours later and its speed smaller than the tidal 

 currents. As a result of such great retardation compared with the semi-diurnal tidal current which 

 occurs in the Laptev Sea, an almost opposite current is observed at a slight depth in the sea. In the 

 case of weak ice drift and strong tidal currents, the top surface of the layer of opposite currents 

 rose almost to the surface of the sea; with strong drift and weak currents it descended deeper. 



In the course of a day the ice, as well as the tidal currents, described closed curves, coun- 

 terclockwise near the mouth of Khatangski Gulf and clockwise in the central part of the sea, far 

 from the distorting effect of the shores. The speed of the tidal drift of ice reached 1.3 knots along 

 the shores. The speed of the tidal drift of ice reached 1.3 knots along the shores and only 0. 7 knots 

 in the open part of the sea. The effect of tides on the drift of ice was especially sharply felt in the 

 spring tides and with little wind. However, even during winds of average force the tidal movements 

 were well marked. 



Figure 120 shows (according to Storozhev), with progressive vectors for various hours of 

 lunar time, the tidal currents at the surface of the sea, at 15 m, and at the bottom, observed at the 

 mouth of the Khatangski Gulf at 74° 44' north, 112° 38' east. Figure 121 shows the tidal currents 

 at the surface of the sea and at the bottom in the open part of the sea at 75^ 26' north, 122° 20' east. 



Figure 120. Semidiurnal tidal currents in the Laptev Sea at 74° 44' north, 

 112° 38' east, 24 and 25 November 1937. 



The observations of the icebreaker Lenin are valuable for their completeness. They have 

 verified previous observations. The basic conclusions which may be drawn from the Lenin obser- 

 vations and from others are as follows: 



1. In the open parts of the sea the tidal drift of ice in the northern hemisphere is in a clock- 

 wise direction. Exceptions to this rule may often be observed near the shores. 



2. The speeds of tidal movements of ice are considerably less than the speed of the tidal cur- 

 rents observed under the ice and considerably less than the speed of surface tidal currents observed 

 in the same region in the absence of ice. 



337 



