sisted of 9/10 concentration of winter and young ice 5 to 7 feet thick. 

 A snow cover 1 to 2 feet thick was observed. Many hummocks, bergy bits, 

 and growlers were present in this area, in addition to some muddy and 

 plankton discolored ice. South of King Island extreme ice conditions 

 were encountered ; a lO/lO concentration of ice up to 10 feet thick was 

 observed, with greater thicknesses in pressure ridges. Progress was 

 extremely slow in this area. 



Ice conditions were more severe than those observed during the 

 spring of 195U» Ice was thicker and less broken and the spring breakup, 

 which was complete in late May in 195U, was only commencing at this time 

 in 1955. 



B. Bathythermograph Observations 



1, Winter 



Bathythermograph observations were made hourly while underway in the 

 Bering Sea and at all oceanographic stations. Observations were in- 

 creased to l5-3iinute intervals over a 30-mile distance when approaching 

 and departing the ice boimdaiy, ice conditions permitting. Representa- 

 tive BT traces depicting typical March and April conditions in the Bering 

 Sea are shown in Figure 22, In the shoal areas over the continental 

 shelf the water is essentially isothennal with depth, but a negative hori- 

 zontal gradient across the ice boundary is evident. In the deeper areas, 

 where warm water is found beneath the colder surface water, positive ver- 

 tical gradients are present in the surface and near-surface layer ap- 

 proaching the ice packj within the ice pack positive gradients are found 

 below a layer of isothermal water. Progressing northward, the temperature 

 inversion is found at greater depths, below which isothermal conditions 

 extend to the bottom, 



2. Spring 



Bathythermograph casts were made at each oceanographic station. Obser- 

 vations were generally obtained hourly while underway. When ice conditions 

 slowed the ship, they were obtained at 10-mile intervals. Figure 23 shows 

 representative BT traces depicting April and May conditions. In the deep 

 central portion of the Bering Sea distinct positive gradients are found, 

 commencing at depths between 100 and 700 feet. Over the continental shelf, 

 the vertical structure is isothermal. Traces taken on 21 April and 27 May, 

 show a gradual warming of the water column, 



C, Meteorology 



Weather conditions in the Bering Sea off North America are primarily 

 the result of the cyclonic circulation of the Aleutism low during the 

 winter and spring seasons. The intensity and extent of this pressure 

 system depends upon the predominance and direction of movement of intense 

 migratory depressions. Warm, moist Pacific air, and cold, dry Arctic air 



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