92 



patterns. This mass of cold water has been partly separated from 

 its source, the Labrador Current, by a thrust of Gulf Stream water 

 from the northern border of the latter current. The separation of the 

 cold water mass from the Labrador Current was not complete in the 

 section under discusssion and the axis of minimum temperature, indi- 

 cated by the broken line in figure 25, readily shows the origin of the 

 cold water at station 2952, and demonstrates the maniier in which 

 similar but completely isolated cold-water masses are formed. 



A secondary axis of minimum temperature is shown in figure 25 

 by the broken line roughly paralleling the bottom in the vicinity of 

 the continental slope. This secondary temperature minimum is not 

 as clearly defined in this section as the shallower axis but it serves to 

 show the effect of cabbeling and downward mixing- along the border 

 of the Labrador Current. 



It is of interest to note here the order of magnitude of the possible 

 increase in depth of a mixture of the contrasting waters at stations 

 2449 and 2450. At station 2449 at a depth of 150 meters the temper- 

 ature and salinity were respectively 4.60° C. and 34.18°/oo resulting 

 in a value of o-,=27.09. At station 2450 the same density surface 

 lay at a depth of about 200 meters where the temperature and salinity 

 were respectively 10.25° C. and 35.23°/oo with a resulting a« of 27.10. 

 If these two waters are mixed in equal proportions the resulting mix- 

 ture will have a temperature of 7.42° C, a salinity of 34.705°/oo 

 and a resulting cr, of 27.15. At station 2949 this density surface 

 lay at a depth of about 187 meters or 37 meters deeper than the com- 

 ponent from this station, and at station 2950 this density surface 

 lay at about 220 meters or 20 meters deeper than its component. 



In the discussion of the cold water mass at station 2952 its connec- 

 tion with the Labrador Current was traced entirely by means of 

 temperatures. Figure 26 bears out the conclusion reached on the 

 basis of temperature, that the w^ater mass in question at station 2952 

 had its origin in the Labrador Current. In this figure lines of equal 

 negative salinity anomaly have been drawn for the same stations 

 shown in figure 25. Labrador Current water is characteristically 

 cold and of low salinity, but further, it is characteristically of high 

 negative salinity anomaly. On figure 26 the axis of negative salinity 

 anomaly has been shown as a broken line. This figure clearly con- 

 firms the Labrador Current origin of the cold water mass at station 

 2952. A secondary axis of negative salinity anomaly has been indi- 

 cated by a broken line and, like the secondary axis of minimum 

 temperature in figure 25, it parallels the bottom near the continental 



2 This opportunity is taken to point out again that in this region the cabbeling and downward mixing 

 which takes place along the current boundaries is characterized by a series of comparatively small depth 

 increments usually accompanied by a relatively large horizontal component of motion so that conditions 

 existing in any vertical section are largely the result of mixing nil along the current boundary for a varying 

 but considerable distance upstream. 



