134 



One of the difficulties with this explanation of the formation of 

 bottom water has been that the bottom water in stnnmer had amounts 

 of dissolved oxygen considerably below the values given by Fox for 

 saturation at the low wintertime temperature required for convec- 

 tional vertical mixing. Figure 55 indicates a solution to this diffi- 

 culty. Smith, Soule, and Mosby have shown that on the basis of 

 summertime measurements of temperature and salinity the maxi- 

 minn temperature at which convectional mixing to bottom could 

 occur, in the absence of horizontal movements, was about 2.0° C. 

 If 90 percent of the Fox "saturation" figure is taken as a fair value, 

 we could expect to get about 6.9 ml. per liter of dissolved oxygen 

 into the water during the convection process. The Baffin Bay 

 water just north of Davis Strait Ridge is known from the Godthaab's 

 measurements to be very low in oxygen. These measurements, 

 verified by the deepest observation of the General Greene at station 

 2838, show that the oxygen content of water crossing the ridge into 

 the Labrador Basin would be about 5.0 ml. per liter. 



Figure 55 shows clearly an oxygen minimum extending from Davis 

 Strait Ridge down the Labrador Basin slope to the boundary be- 

 tween the intermediate water and deep water (between about 2,000 

 and 2,500 meters) and indicates the movement of Baffin Bay water 

 into the Labrador Basin. If such water is mixed with the Labrador 

 Basin water with an oxygen content of 6.9 ml. per liter in a pro- 

 portion as much as one-quarter Baffin Bay water to three-quarters 

 Labrador Basin water we come out with an oxygen content of the 

 mixture of 6.4 ml. per liter, which is about the value shown in figure 

 55 for the bottom water in the Labrador Basin. 



Presumably such a contribution of Baffin Bay water is not con- 

 fined to the brief season during which convectional mixing is pos- 

 sible but continues after the vertical convection stops, thus estab- 

 lishing the oxygen minunum shown in figure 55. It should be empha- 

 sized in considering this Baffin Bay contribution that south is not a 

 major component of its motion but the result is attained through 

 lateral mixing. 



Smith, Soule, and Mosby have also shown that to qualify as a 

 constituent of the bottom water, ihe vertically mixed water should 

 have a salinity between about 34.81 and 34.91 7oo- It has been 

 shown that the mean salinity of the water colunui in this region is 

 about 34.88 7oo in summer. Station 2838 shows that the water, 

 near bottom on the ridge has a summertime salinity of about 34.60 7oo- 

 A mixture of waters of such salinities in the above-mentioned pro- 

 portion would result in a salinity of the mixture of about 34.80 %o 

 which closely approaches the limit of 34.81 °/oo- 



It must be remembered in connection with the above discussion 

 that as the contribution from Baffin Bay proceeds from Davis Strait 



