With further cooling of the sea surface, the lower boundary of vertical circulation, dropped 

 even more. But here, naturally, the water above the top of the bank cooled somewhat more and 

 correspondingly its density becomes somewhat greater than above deeper places. As a result, the 

 colder deeper waters start to creep down the slopes of the bank until they drop to the level with 

 equal density. In turn, the creep of the water from the slopes is compensated for by a rise in the 

 deep waters which creates circulation, as Indicated in figure 20 by the arrows. 



We should note that such a pnenomenon is of considerable significance only when the surface 

 layers of the sea have comparatively high initial temperatures. Actually, we have seen that with 

 temperatures close to the freezing point, a temperature change has practically no effect on density. 

 It is a different story when vertical circulation is accompanied by ice formation and the salinity in- 

 crease which goes along with it . 



If the depth of the bank is less than the critical depth of vertical circulation, the temperature 

 of the water above it drops to the freezing point sooner and ice formation starts earlier. 



Further, we have seen that the salinity increase in the sea during ice formation, if we assume 

 the salinity of ice to be , is determined by the formula 



AS-. 



0.9 / 

 P 



S, 



where i = the thickness of the ice, 



5 = the salinity of the water from which the ice forms, 

 p = the depth of propagation of vertical winter circulation. 



Assuming that the initial salinity is 15 o/oo and the thickness of the ice forming in winter is 

 2 m, which is common for the regions of the New Siberian Islands, for example, we find that toward 

 the end of winter the salinity at the 10 m depth has increased to 17. 6 o/oo and at the 5 m depth, to 

 20.4 o/oo, which gives, in the first case, a natural density of 14. 12, and in the second case, 16.38. 

 Understandably, such a large difference in densities unfailingly involves creep of cold and more 

 saline waters to deeper locations or, at least, to deeper levels. Naturally, such phenomena are 

 observed off-shore, particularly in shoals and are realized to a very great extent in the frozen 

 reaches of the ocean, particularly in the Arctic Basin. 



LITERATURE: 62, 77. 



Section 33. The Cold Intermediate Layer 



The vertical winter circulation continues as long as cooling does, and at the moment it ceases, 

 it is characterized by the amount of heat released by the sea, by the thickness of the mixed layers, 

 and by their overall temperature. The latter, in the case of ice formation, naturally is equal to the 

 freezing point, while in the absence of ice formation, depending on the vertical salinity gradient it 

 may be either higher or lower than the temperature of the lower lying layers. 



Let us assume, as In the majority of cases, that the temperature of the mixed layers is lower 

 than the temperature of layers not affected by vertical circulation (temperature inversion) and let 

 the lower circulation boundary at the moment it ceases, be defined by depth p' . In this case, the 

 vertical temperature distribution is represented schematically by curve abed (figure 21). Let us 

 further assume that at this same moment summer heating of the upper sea layers begins, gradually 

 extending to greater and greater depths. Correspondingly, (If the heating proceeds under calm con- 

 ditions) the upper layers heat through and the vertical temperature distribution is shown by curve 



80 



