Table /.-Average nutrient concentrations (/jg-at/1) in 

 the North Slope rivers and icemelt from the Beaufort 

 Sea 



*Trace Amount 



20 kts in the southern Beaufort Sea (U.S. Navy 

 Hydrographic Office, 1968). 



During WEBSEC-71 and 72, surface winds 

 exceeded 20 kts only five times and then only for a 

 period of a few hours (figs. 27-28). The effects of 

 wind mixing on the surface waters seemed to be 

 limited to the upper 30 meters of the water column 

 (figs. 32-37, 44-55, 62-67, 74-49, 86-97). Low 

 surface salinities ( <28°/oo) in the ice-free areas 

 indicate poor wind mixing. Sater (1969) states 

 that surface salinities in ice-free areas should 

 rarely be less than 28°/oo because of wind mixing 

 of icemelt or river runoff with underlying sea 

 water. Variations in the surface wind field during 

 1971 included two periods of moderate (up to 25 

 kts) winds (September 1-5, STA's 46-58: and 

 September 13-16, STA's 86-93) separated by 

 periods of relative calm (<10 kts) (fig. 27). Both 

 moderate wind periods were associated with a 

 decrease in barometric pressure (fig. 29). 



Surface air temperature did not show any clear 

 trend toward decreasing values during the length 

 of the 1971 cruise (fig. 29). The largest tempera- 

 ture change observed was 6° ( — 3.0 to 3.0°C). The 

 coldest surface air temperatures ( <0°C) were as- 

 sociated with NW to NE winds, while the warmest 

 values are associated with southwesterly winds. 

 Some variation in air temperatures during any 

 period of the cruise probably results from varying 

 proximity to the edge of the ice pack. 



Variations in the surface wind field during 

 WEBSEC-72 are not as detailed due to the lack of 

 data but trends are still discernable (fig. 28). 

 Wind speeds were again less than 20 kts and 

 predominantly from the NE except for two periods 

 of moderate winds (August 8-10 W-SE, STA's 

 12-17, September 12, W-NW, STA's 60-61) 



where speeds up to 25 kts were measured. An 

 increase in barometric pressure occurred during 

 both periods. Warm surface air temperatures 

 were associated with the W-SW winds whereas 

 cold surface air temperatures were associated 

 with the W-NW winds. 



Surface air temperatures showed a trend to- 

 ward decreasing values during the 1972 cruise 

 (fig. 30). There were two periods of warming 

 (August 19-22, September 2-5) though the latter 

 was not as high in temperatures. Air temperatures 

 were generally much higher ( —2 to 10°C) in 1972 

 than in 1971 (-3 to 3°C). 



Below the summer convective layer, a subsur- 

 face temperature minimum ( — 1.1 to — 1.5°C) 

 layer of 5 to 10 meters thick was observed at many 

 of the northern and eastern stations taken during 

 WEBSEC-71 and 72 (figs. 32 and 33). The 

 minimum layer was found from 15 meters to 40 

 meters depth. Salinities associated with the 

 temperature minimum ranged from 30. 1 to 

 32.2°/oo (fig. 35). This cold layer situated be- 

 tween the warmer upper and lower layers forms a 

 dischothermal temperature stratification that is 

 probably due to a limitation of the convective 

 process and is unaffected by depth of water. De- 

 fant (1961) states that if salinity is not nearly 

 constant at all depths of the water column, the 

 convective processes in the autumn and winter 

 will not be able to extend to the bottom. With the 

 onset of spring, heating of the surface layer begins 

 and gradually extends to greater depths during 

 the summer. However, if summer heating is not as 

 intense as winter cooling, then a cold inter- 

 mediate layer if formed and can be interpreted as 

 the remainder of the convectional flux extending 

 to the depth during the winter. Thus the depth of 

 convectional penetration in winter of the western 

 Beaufort Sea is, in general, limited to less than 40 

 meters. 



The temperature minimum layer was evident in 

 the eastern area of the western Beaufort Sea 

 throughout the length of the 1971 and 1972 

 cruises, indicating that the layer exists through- 

 out the summer (figs. 50, 86, and 92). The ab- 

 sence of the layer in the western section of the 

 survey area is probably due to advection of a warm 

 layer into the area. This warm layer will be dis- 

 cussed in a later section. 



9 



