It is apparent that the diverging outflow into a large seaway is not 

 continuous and that any static representation can only imply an average 

 state, about which the natural state varies. The present oceanographic 

 instrumentation is not adequate to follow these short-period variations, 

 ■even the salinity-temperature-depth recorder(5) will require some 

 improvement before this is possible. x\t present it is necessary to make 

 a series of observations at small intervals of time until enough data is 

 collected to evaluate a reliable statistical mean of the structure. The 

 additional time required almost vitiates the possibihty of making a 

 synoptic survey of an extensive area, where functions of tide, wind, and 

 run-off must also be considered. It is probable that the only satisfactory 

 approach to this problem is by model studies. A model of Alberni 

 Harbour(ll) was made in which the geography, tide, and river discharge 

 were simulated and was successful in reproducing all the features of the 

 outflow which have been discussed. This indicates a practical approach 

 to the study of seaways where the boundary conditions can be represented. 



The Ocean Outflow 



When the outflow enters a large seaway or ocean it tends to form a 

 jet stream(lO) which veers to the right or left in response to the Coriohan 

 force (11), at least in the middle and polar latitudes, and moves coastwise, 

 contrary to the great ocean currents. This is more of a gradient flow 

 along the isobars than a displacement flow across the isohalines. 



Figure 9 shows an interpretation of the dynamic topography off the 

 Pacific Coast of Canada (8) which may be regarded as representative, 

 since the illustrated coastal current has been observed empirically, and 

 qualitatively related with the local seasonal run-off(7) and the Japan 

 current off-shore corresponds with what is known of this movement from 

 casual and experimental drift observations (12). 



Evidence of cloud structure in the surface waters of the open sea have 

 been observed (14), but in general the fluctuations in properties of the 

 water are small compared to those in the immediate vicinity of an outflow. 

 In general, the shallow and irregular upper zones tend to obscurity in short 

 distances because of the accelerated mixing by the considerable wind 

 forces. Once this simplification has taken place the structure appears 

 to be very stable and to degrade along the line of flow by a somewhat 

 similar process to that observed in the simple system. 



This is illustrated in Fig. 10, which shows a series of salinity gradients 

 observed at regular intervals through 180 kilometres off the Pacific 

 Coast of Canada. These stations correspond to the numbered positions 

 in Fig. 9. They were observed while proceeding seaward on 20th July, 

 1936, and again during the return journey the next day, and both data 

 are indicated in the figure. 



The lower boundary is taken to mark the effective depth of wind 

 mixing along the course of the Japan current in the open ocean, and the 

 intermediate layer to represent the character of this water. The upper 

 zone is shown to be continuous with the coastal system and represents 

 the influence of local fresh water in the great ocean current. 



This also implies a transfer of water across the isobars — that is, 

 there is a component of flow normal to the isohalines, corresponding to 

 the displacement flow of the simple S3''stem. Evidently both the gradient 

 and displacement tendencies must continue to exist at all times. , In the 

 two-dimensional channel the gradient flow is limited by the boundaries 



285 



