Figure 8a. Circulation of surface com- 

 puted relative to the 500-meter surface. 

 Dynamic height anomaly extrapolated 

 into shallow water at stations 2 and 30. 



CIRCULATION 



The surface currents resulting from the distri- 

 bution of mass — this excludes tidal currents and 

 wind drift currents — are indicated by the dynamic 

 topography of the surface over the 500-decibar sur- 

 face (fig. 8a). Ideally, the reference surface should 

 be at the depth of no motion, so that the computed 

 currents would be the true currents caused by the 

 distribution of mass. The 500-decibar surface has 

 been used here because few data are available 

 below that depth along the northwest line of sta- 

 tions. Where data are available to the 1000-decibar 

 surface, at which the currents are negligible, 2 the 

 pattern of surface current referred to this surface is 

 not changed and the speeds are increased only 

 about 15 per cent. 



North of the Andreanoff Islands is an easterly 

 flow of about 0.15 knot which backs to northeasterly 

 and starts toward the Pribilof Islands. At the 55th 

 parallel it meets and reinforces a strong westerly 

 flow of 0.3 knot off the shelf forming an eddy con- 

 figuration apparently returning toward the shelf. 

 Unfortunately our observations do not extend far 



enough to indicate whether it again turns north- 

 westerly or flows onto the shelf. 



The surface salinity distribution (fig. A2b) agrees 

 well with the currents from the dynamic topography. 

 A pronounced tongue of low-salinity water (less than 

 33.00 °/oo extends into the Bering Sea with its axis 

 along the strong westerly flow. The dynamic topog- 

 raphy of the 150/500 decibar surface (fig. 8b) indi- 

 cates at 150 meters a weaker but similar circulation 

 — about 40 per cent of that at the surface — which 

 would indicate that this westerly flow and associated 

 low-salinity tongue is not a shallow transient feature 

 but a semipermanent feature of the circulation. The 

 weak southeasterly flow indicated in the western 

 part of the region confirms the interpretation given 

 earlier of the movement of water at the temperature 

 minimum. 



With reference to previous conclusions as to 

 currents, the weak westerly component of 0.1 knot 

 found by Barnes and Thompson 2 about 40 miles 

 north of the Andreanoff Islands did not appear as 

 a widespread feature in our observations, although 

 station 22 seems to be associated with a small eddy. 

 It can be concluded that this westerly component 

 was probably associated with a small feature evi- 



