US/USSR BERING '88 

 CHUKCHI/BERING STRAI" 



CHUKCHI 



10 



/- 5 



30 31 32 



SALINITY (ppt) 



Fig. 4a. All CTDdata(l-m average values) from Bering Strait and southern 

 Chukchi Sea. 



and fresher it becomes; this accounts for the trend of data points 

 in Fig. 4a from about 3°C. 32 ppt. toward 12°C, 30 ppt. The 

 flow is northward parallehng the coast, then through the 

 eastern channel of Bering Strait, where its characteristics are 

 illustrated by Station 79. Thus, the modification of the waters 

 on the eastern side of the basin involves both lateral and vertical 

 mixing. Salinities are reduced by about 1 ppt in transit through 

 admixing with fresher waters closer to shore, ultimately of 

 course due to substantial coastal runoff As temperatures are in 

 general higher in the shallower waters near shore, the lateral 

 mixing also gives rise to some warming. Water temperatures 

 are also increased through vertical mixing, as with the waters 

 on the western side, and undoubtably the warming is more 

 effective in the shallower waters of the eastern side. Between 

 the two effects, T increases are of the order of 3°C. We note that 

 the mixing processes on the eastern side are diapycnal, leading 

 to decreases in water densities, which is not true of the 

 modifications in the west. The reason for this is the difference 

 in effects of salinity and temperature on density, salinity is 

 much more important in "controlling"" density in cold water 

 (cf slopes of isopycnals in Fig. 2b). 



Chukchi Sea 



All CTD data from the Chukchi Sea are plotted in Fig. 4a. 

 Similarly to the Chirikov basin, there is a concentration of 

 bottom values in the salinity range -32.2 to 32.9 ppt, but the 

 temperatures of this water are slightly warmer than to the south, 

 ranging from ~ 1 .5 to 4°C. From this concentration, data points 

 extend in two directions. One trend is toward warmer and 

 fresher, toward ~10°C and 30 ppt, much like the trend in the 

 Chirikov basin data (cf. Fig. 3a). These data are from the water 

 masses that have entered the Chukchi Sea from the south, 

 through the Bering Strait; salinities have not been modified 

 appreciably since transiting Bering Strait, but the small warming 

 indicates that heat continues to be added to the bottom water 

 through vertical mixing. 



WEST OF PT HOPE 

 49\-\48 



SALINITY 



Fig. 4b. As with Figs. 2b, .^b, but illustrating the major water mass modifications 

 occurring in the southern Chukchi Sea. The later and vertical mixing 

 processes found in the eastern part of the Chirikov basin continue to 

 modify the water masses How ing northward through Kotzebue Sound 

 and passed Pt.Hope. A colder, more saline water mass indigenous to 

 the Chukchi Sea is advected southeast by the Siberian Coastal 

 Current, then circulates cyclonically and mixes with the water flowing 

 north through Bering Strait. 



The other trend is toward a colder and more saline water 

 type, -33.5 ppt and 0°C. This is water that appears nowhere 

 south of the Bering Strait, so must be indigenous to the Chukchi 

 Sea. The only water south of Bering Strait with S>33 ppt is in 

 the Gulf of Anadyr and was not observed north of Anadyr 

 Strait, which positively rules out the northern Bering 

 Sea as a possible source for this relatively cold, high salinity 

 water. 



Key stations illustrating the water masses in the southern 

 Chukchi Sea are plotted in Fig. 4b. The current flowing 

 northward through Bering Strait trends eastward into Kotzebue 

 Sound, then tuins north and west and Hows passed Pt. Hope 

 into the northern Chukchi Sea (cf. Coachman ct al., 1975, 

 Chap. 4). The core of flow of this water, that with the highest 

 salinities, is water transitting the western channel of Bering 

 Strait (Stations 76-78; cf Fig. 3b). This water is observed west 

 of Pt. Hope at Stations 48 and 49. The water east of this core 

 tlow. between it and the Alaska coast (represented west of 

 Pt. Hope by Station 50), is all less saline and warmer, and 

 creates the data trend exposed in Fig. 4a. In traversing Kotzebue 

 Sound (a distance of -350 to 400 km) salinities of the core 

 water have been reduced a little, about 0.2 to 0.3 ppt, and 

 bottom temperatures have been increased a further 0.5°C. 

 Thus, both vertical mixing and a small amount of lateral 



32 



