conditions represented by the dynamic topography, instantaneous 

 current vectors would result from the GEK observations. These 

 were considered to be the sum of the steady state and the momen- 

 tary value of fluctuating- currents. The fluctuating currents were 

 expected to include periodic currents, such as tidal currents, and 

 aperiodic currents, such as transient wind effects. To simplify 

 the interpretation of the comparison as far as possible the first 

 part of the June survey of 1950 was selected as having been made 

 during exceptionally quiet weather when wind effects were as- 

 sumed to have been negligibly small. 



The above described method was used to compute equivalent dif- 

 ferences in dynamic height, station to station, from the GEK obser- 

 vations (AD GEK) for stations 4175 to 4205 and compared with the 

 differences in dynamic height of the surface above the 1,000-decibar 

 surface (AD 1,000 deb) . The disagreement between the GEK and 

 dynamic topography was of the same order of magnitude as in the 

 1948 measurements. To see if there were any relation between 

 AD GEK and the density distribution two plots were made, one of 

 AD GEK - AD 1,000 deb versus AD 1,000 deb, and the other 

 AD GEK — AD 1,000 deb versus gradient as determined from the 

 dynamic topography. Both plots showed a random distribution of 

 points with no evident relationship. 



In order to study the general trend of AD GEK, cumulative plots 

 were made of AD GEK, AD 1,000 deb, AD 1,500 deb and AD 2,000 deb 

 against distance. These plots showed that, although in general the 

 profile of the sea surface thus constructed from the various deriva- 

 tions of AD tended to be similar, errors at any one point were masked 

 by the fact that the curves were displaced from one another be- 

 cause of the cumulative differences in the values for each station 

 interval. 



To better examine the station to station differences, lines of AD 

 GEK - AD 1,000 deb, AD GEK -AD 1,500 deb, AD GEK -AD 

 2,000 deb and AD GEK (uncorrected for drift) — AD 1,000 deb were 

 plotted against distance. Disregarding the magnitude of the pro- 

 portionality constant, there was little to choose between the different 

 reference levels of dynamic computation in comparison with the 

 GEK. Observations permitting the use of the deeper reference 

 levels, however, were available only from the southern part of the 

 survey. This southern section showed, surprisingly enough, that 

 variations between the GEK and the dynamic heights were smallest 

 in the area of shoalest water, a finding which is probably coinci- 

 dental. 



The proportionality factor of the current meter varied widely 

 from station to station and was less than unity at 22 of the 30 



34 



