ESTUARINE MODEL OF SUB-ARCTIC PACIFIC OCEAN 441 



The NORPAC (1955) data, recorded in the Oceanic Observa- 

 tions of the Pacific (Reid et al., 1960), show that the halocline 

 structure is continuous across the ocean north of the sub-Arctic 

 boundary from Asia to America. Little is known of the lower zone 

 circulation in mid-ocean; but, in the eastern Pacific, between 

 Ocean Weather Station "P" and the Canadian coast, Bennett 

 (1959) has shown a persistent intrusion of deep water. Thus at 

 least one region of deep inflow is recognized. 



Figure 6 shows that, in the eastern sub-Arctic, the amount of 

 fresh water is greatest around the North American coast. From 

 there the most direct route of transport, to the region of dissipation 

 in the sub-Tropics, would be southward. However, because of the 

 Alaska Gyral (Fig. 7) the direct southward route is denied to much 

 of this water. Similar local centers of fresh water concentration 

 occur in the Bering and Okhotsk Seas in gyrals contrary to the 

 shortest routes of dissipation. Evidently fresh water transport 

 mechanisms are present in the sub-Arctic Pacific Ocean. However, 

 wind-driven and other mechanisms are also present, and determine 

 the paths of flow within the region. 



In the estuarine model previously described by Tully (1958) the 

 requirements for net outward transport in the halocline, and net 

 inward transport in the lower zone, and a shear zone in the halo- 

 cline to provide energy for entrainment, were all accomplished by 

 assuming opposite directions of flow in a narrow embayment, and 

 a layer of no net transport in the halocline. 



However, the required conditions are provided if the volume 

 transport decreases along the path of transport in the lower zone, 

 and increases along the path of transport in the upper zone and 

 halocline, as sea water is entrained. Bennett (1959) showed that 

 there were shear zones in the depths of the halocline (upper 200 m) 

 over most of the Gulf of Alaska. Doe (1955) also observed this 

 feature. 



Conclusion 



It is concluded that the features of an estuarine region, the 

 salinity structure, the entrainment process, and the fresh water 

 transport mechanism, are realized northward of a sub- Arctic 



