structure maintains itself but the warm layer thins as cooling pro- 

 gresses. Wave action accounts for the mixing of the upper layer; 

 thinning of the upper layer appears to be due to thickening of the sub- 

 thermocline layer rather than to mixing of heat downward. Geostrophic 

 forces associated with an easterly current component could cause this 

 condition. We picture here the possible existence of a cyclonic gyre 

 in the northern Chukchi as suggested by Aagard and Coachman (1964) 

 and by the ice drifts reported by Garrison and Pence (1973) . 



The cooling toward the north could be due to a loss of heat 

 to the atmosphere or to the presence of diffuse ice in the recent past. 

 In this connection note the long tongue of ice extending south along 

 this line of stations according to the ice report of August 2, one day 

 earlier, as shown in Fig. 32. One might also consider it possible 

 that the flow is toward the south or southeast and that warming takes 

 place as the water drifts southward. This must not be true or the ice 

 would drift southward in the presence of the predominantly westerly 

 winds prevailing at the time (See Appendix I for wind data) . 



Figure 39 continues this series of Fig. 38 across the ice 

 interface. At Station 47, 3 miles inside the ice margin, most of the 

 near-surface warmth was gone. However, it is interesting that all 

 the profiles of this series, even to 18 miles inside the margin, were 

 warmest at the surface. There was little mesostructure . 



Another crossing in the same area is shown in Fig. 40. The 

 conclusion is similar but, at and just within the ice boundary, cooling 

 at the surface was sufficient to produce a small "warm" nose. The series 

 of Stations 66 to 74, Fig. 41, another crossing of the ice margin in the 

 east-central part of the area, lead to similar conclusions. 



The sequence of Stations 22-28, Fig. 42, 65 miles from the 

 coast is somewhat similar. The warm nose maintains itself a little 

 better, there is structure in the depth zone which was warm, but not 

 much warmth was retained at the 5-mile penetration. Station 28. 



In the coastal current, the picture which developed in 1971 

 was one in which the warm layer maintained itself with little tempera- 

 ture decrease until it encountered ice. Then the remanants of the layer 

 were still maintained at depth after many miles of travel under the ice. 

 Mesostructure was frequent and sometimes prominent. The series. 

 Station 106-114, already illustrated, also adheres to this type. 



The difference in the westerly stations may most easily be 

 accounted for by a difference in the rate of flow of the warm water. 

 West of the coastal current one sees a layer of warm Bering Sea water 



60 



