near the Alaskan Peninstila. In the open water north of Unimak Pass the 

 surface water temperature was approximately 1.7°C warmer on 27 May 

 (station 2?) than it was on 21 April (station 1), Vertically, tempera- 

 tures in the open water south of the ice pack (Fig, 13) increase with 

 depth to 500 meters. In the deep water off the she3jC the positive ver- 

 tical gradient is steepest at depths of iSO to 250 meters. Below this 

 depth water temperatures decrease gradually. The teu^jerature structvire 

 across the ice boundary in spring (Figs, Ik and 15) is similar to that 

 observed in winter. In the deeper waters (Fig, lU)* positive vertical 

 gradients were observed beneath the ice and south of the ice bovindary. 

 Over the shelf areas (Fig, l5)> isothermal conditions prevailed with 

 strong horizontal gradients south of the ice boundary. Within the ice 

 pack (Fig, 16) temperature conditions remained isothermal, 



2, Salinity 



Surface salinity distribution during spring 1955 is shown in Figure 

 •12, Salinity decreases from the southwest to the east and northeast. 

 This change from the deeper waters of the southwest to the shallow waters 

 over the shelf is similar to that observed in winter, but the values at 

 given positions are higher in spring, indicating the northward penetra- 

 tion of more saline water following the retreating ice edge. Little 

 seasonal change is evident northeast of St, Lawrence Island, where salinity 

 values tend to remain slightly higher than those observed southeast of the 

 island. 



Cross sections depicting the vertical distribution of salinity are 

 presented in Figures 13 through 16, In deep water, salinity increases 

 with depth. In shallow water, salinity conditions are nearly isohaline. 



The higher values northeast of St, Lawrence Island are apparent in 

 Figure 15 (stations 20, 21, and 22), 



3. Density 



Density characteristics during spring follow much the same pattern in 

 shallow and deep waters as observed during the winter season (Figs, 13 

 through 16), 



U, Sound Velocity 



Surface sound velocity (Figs, 13 through 16) ranged from U,702 ft, /sec, 

 (stations 13, lU, and 15) to 1;,789 ft./sec, (station 28) in open water 

 south of the ice pack. The maximum subsurface sound velocity observed was 

 [i,9U7 ft./sec. at a depth of 3,068 meters (station 6), No definite sovnd 

 channel could be defined. 



16 



