The Representation of Oceanic Movements and Kinematics 



355 



typical cases that the permanent current of the deep North Polar Basin flows first 

 at 1-0 cm/sec N. 64° W. and later at 2-1 cm/sec S. 12° W. Brennecke (1921) and 

 SvERDRUP (1928, \93>\b) later used the same method to show from the ice-drift 

 observations of the "Deutschland" and the "Maud" that there is no permanent surface 

 current in either the Weddel Sea or off the North Siberian Shelf. 



Later, Sverdrup developed another method that makes use of all the available wind 

 and current observations. The vectorial resultant of the current is calculated for wind 

 groups concerning certain directions (for example, four groups with the wind for each 

 quadrant centred on N., E., S. and W.) and divided by the wind strength of each 

 group to give the "relative" resultant current (for 1 m/sec wind). If a pure drift current 

 is present then the resultant of the current vectors of all the wind groups must vanish, 

 since they will be symmetrically grouped around the zero point. If, however, the ob- 

 served current is made up of wind drift + basic current, the resultant of all the groups 

 will not be zero but will represent the basic current. If a coasthne impedes the de- 

 velopment of the wind drift equally in all directions and favours a current parallel 

 to the coast, then the circle connecting the ends of all the current vectors will be 

 replaced by an ellipse (Witting, 1909). 



Table 114. 'Tram" Expedition: 27 May 1895 - 27 June 1896. Ice drift 

 grouped according to the directions of wind resultants 



Table 114 contains the ice-drift observations of the "Fram" for the period from 27 

 May, 1895 to 27 June, 1896 (Fig. 148) according to Sverdrup. The diagram on the 

 left of Fig. 148 shows that the end-points of the vectors lie on a circle, but that the 

 centre of the circle is not at the zero point but is displaced in the direction S. 82° W. 

 Vectorial subtraction of the basic current (0-79 cm/sec, bearing 262°) results in the 

 diagram given on the right of Fig. 148. The velocity 0-79 cm/sec refers to a wind speed 

 of 1 m/sec. During the year, however, the mean wind speed was 2-80 m/sec, so that 

 for the period under consideration there was a permanent surface current of 2- 

 cm/sec along a bearing of 262° (direction relative to the 75° E. meridian). Nansen 

 obtained by his method 2-0 cm/sec on a bearing of 256° which is in satisfactory agree- 

 ment. The table shows that the relative wind drift is practically independent on the 

 direction of the wind ; the mean of the four groups shows that a wind with a strength 

 of 1 m/sec gives rise to a surface drift of 1-67 cm/sec deflected 30-5° to the right of 



