is nearly constant between 100 and 150 meters and 

 the depth increases as the minimum degenerates. 



The uniformity of temperature at the maximum 

 is indicated in figure 7a. The depth of the maximum, 

 figure 7b, is less significant than that of the minimum 

 because the maximum is very flat, but a trend is 

 observed similar to that of the depth of the tempera- 

 ture minimum. Below this maximum, both the hori- 

 zonal and the vertical gradients of temperature and 

 salinity are small. 



Possible explanations of the temperature mini- 

 mum are: (1) it is the result of winter cooling and 

 convection currents to the depth of the minimum; 

 (2) it is caused by deep water forced towards the 

 surface in some manner; (3) it is the result of a flow 

 from another region. 



At first sight, it would appear that the tem- 

 perature minimum represents the depth to which con- 

 vection currents penetrated in winter, especially when 

 it is also noted that the salinity becomes nearly 

 constant at and above the temperature minimum and 

 that the oxygen content is relatively high to this 

 depth. However, the average minimum temperature 

 of the mixed layer in this region during the winter 

 is about 2.8° C. 7 It therefore seems improbable, even 

 assuming below-normal winter temperatures, that the 

 minimum temperatures of 2° C and less observed 

 during the summer at depths less than 200 meters 

 can be explained solely by winter cooling. 



The possibility that the water is deep water 

 forced toward the surface by topographic features 

 or other cause is ruled out by its low salinity. There 

 then remain to be examined possible sources from 

 which a flow of cold low-salinity water could occur 

 to reinforce the effect of local winter cooling. 



The aforementioned degeneration of the tem- 

 perature minimum from the Okhotsk Sea seems to 

 rule out the possibility that any water moving into 

 the Bering Sea between the Komandorski and Near 

 Islands and east along the ridge would be respon- 

 sible for the minimum. In fact, it was suggested by 

 Sverdrup 14 that "this water (at the Carnegie Sta- 

 tions) of very low temperature probably comes from 



14 J. A. Fleming et a/... Observations and Results in Physi- 

 cal Oceanography (vol. I-B of Scientific Results of Cruise VII of 

 the CARNEGIE during J928-I929 under Command of Captain 

 J. P. Ault; Oceanography), Carnegie Institution of Washington 

 Publication no. 545, Department of Terrestrial Magnetism, 1945. 



the Bering Sea, where it has entered the Pacific 

 Ocean, and partly spread toward the east." 



The origin of the cold water thus appears to 

 be in the Bering Sea which has ample areas for the 

 formation of such a water type in the Bristol Bay 

 area, Olyutorski Gulf, and the Gulf of Anadyr- 

 Norton Sound area. Barnes and Thompson 2 have 

 eliminated the Bristol Bay area, as a possible source, 

 and this is confirmed in the present data by the 

 configuration of the minimum. The Gulf of Anadyr- 

 Norton Sound area, which is the most extensive of 

 the above, is almost solidly covered with young sea 

 ice during the winter. 1 "' Observations of February 

 1 951 le showed vertically uniform water of a tem- 

 perature of — 1.75° C and salinities around 32.5 °/oo 

 to 33.0 °/oo in the region of the young sea ice 

 north from St. Matthew Island and around St. Law- 

 rence Island. Comparable conditions probably occur 

 throughout the ice-covered regions along the Siberian 

 coast which include Olyutorski Gulf. A source in 

 these regions would be in agreement with the con- 

 figuration of the feature indicating movement from 

 the northwest (figs. 2a and 5) and with the T-S re- 

 lations (fig. 3) which show that it would have a 

 salinity of about 33.1 °/oo and temperature of less 

 than 1.3° C. During the summer, water of less than 

 0° C has been observed to the southwest of St. 

 Lawrence Island on several occasions but as a sub- 

 surface mass having less vertical extent. Although 

 surface heating probably accounts partially for the 

 decrease in thickness, some sinking and spreading 

 of this winter water mass could easily occur because 

 of the surface spreading of warmer low-salinity 

 coastal waters which develops during the spring and 

 summer. The present observations thus indicate that 

 the minimum is created, at least partially, by the 

 slow spreading of cold water at subsurface depth 

 south and southeastward in a counterclockwise arc 

 from the coast of Siberia or northern Bering Sea 

 into the southeastern Bering Sea. A corollary to the 

 above interpretation is that the minimum is a wide- 

 spread feature existing throughout the major portion 

 of the deep Bering Sea in summer. 



15 Hydrographic Office, fee Atlas of the Northern Hemi- 

 sphere, H. O. Publication no. 550, 1946. 



16USS BURTON ISLAND (AGB-1), Bering Sea Expedition, 

 Winter 1951 (CONFIDENTIAL), March 1951. 



