506 



Ocean Currents in a Non-homogeneous Ocean 



Helland-Hansen (1939) and others. The surveys made in the southern part of the 

 Norwegian Sea during June/July 1935 (station interval 20 nautical miles) and June/ July 

 1936 (station interval 10 nautical miles) have show^n strikingly large changes in the 

 appearance of different water types which must be due to both, to changes in time and 

 to local variations over short distances. In most cases they could be most probably 

 related to stationary, and in some cases also to progressive vortices. Such disturbances 

 are apparently characteristic of many more intense ocean currents in which there may 

 be waves and vortices of larger dimensions. 



As in the Norwegian Sea, large and regular local variations, as well as variations in 

 time of the different oceanic factors, will also be present in the open ocean, especially 

 in the upper layers, and for larger distances between the stations these can introduce 

 an unpleasant degree of uncertainty for the dynamic preparation of the data. Only by 

 this can it be understood why discrepancies between the results of different investi- 

 gators for a particular area occur and why representations of the same oceanic region 

 often deviate widely from each other. Helland-Hansen has presented an instructive 

 schematic example showing how difficult conditions may be. 



Figure 234 shows two neighbouring profiles / and // through a strong current taken at 

 two different times A and B. The vertical lines represent the position of the stations on 



A*B 



Fig. 234. To the critical discussion of a joint scientific use of observational data, which are 

 gained in a non-synoptical way. 



which the profiles are based, which were different in both cases. In the first survey (^4) 

 the horizontal section at a level k was obtained directly from the vertical profiles. 

 The curves represent isotherms, isosteres or similar curves. Below this are shown the 

 conditions of the second survey {B). Thus it is assumed that the current was the same 

 during both surveys, but that at the time of the second survey it had been displaced 

 relative to the first survey somewhat to the right. In an oceanographic survey in the 



