DAVIS STRAIT AND LABRADOR SEA 21 



The velocity of the current between any two points has been com- 

 puted in the manner described by Smith (1926) (p. 31). 



The extensive use of velocity profiles as illustrations in this paper 

 justifies a description of the method of construction and also refer- 

 ence to the method of computing the volume of the current, or the 

 transport, as it is often called, through any given vertical section. 



A velocity profile is a representation in vertical cross section of 

 the distribution of the components of velocity of the horizontal cur- 

 rents perpendicular to the plane of the section. Equal values of 

 velocity are connected and expressed usually in terms of centimeters 

 per second. As an example we have selected section A, figure 3, a 

 section normal to the West Greenland Current taken off Cape Fare- 

 well, Greenland, September 2-3, 1928. (See station tables, stations 

 1080 to 1086 (pp. 219-220).) 



It is assumed that the mean velocities between successive pairs of 

 stations for a number of standard depths have been computed in 

 accordance with the equation — • 



_ (Ea—Eb) 

 ^~2w • L -sin <f> 



where (Ea — Eb) denotes the average slope of the isobaric surfaces 

 between stations A and B ; w, the angular velocity of the earth ; L, the 

 distance between the stations, and (f>, their mean latitude. These 

 values of mean velocity are then plotted to scale against horizontal 

 distance along the section and with regard to the direction of the 

 component at right angles to the section, figure 3, as a series of 

 parallel lines. 



A smooth curve representing the velocity at any point on any one 

 of the given levels, stations 1080 to 1086, may be substituted for the 

 series of mean velocity lines, provided that (a) the curve be drawn 

 in such a manner between adjacent stations that equal areas are 

 formed on either side of the previously fixed lines of mean velocity 

 and (&) that the curve be drawn flattest near the margin, and near 

 the axis, of each indicated band. Between stations 1080 and 1081, 

 figure 3, for example, the velocity curve is drawn so that the area 

 BEF equals area FAG', and between stations 1081 and 1082 DGH 

 and ICJ equal area P. The velocity curve MN, figure 3, is thus 

 continued to include the remaining stations of the section, and simi- 

 lar curves are constructed for other levels. 



The final step is to project the curve MN, and the curves for the 

 other levels, on to their respective depths in a vertical plane and 

 lastly to connect equal values of the same sign. The resulting illus- 

 tration (see upper half of fig. 3) is referred to as a velocity profile. 



In order to test the accuracy of the above-described method, the 

 dynamic height of a station located midway between stations 1081 

 and 1082 was computed on the basis of temperatures and salinities 

 interpolated from the profiles of these variables. The values of the 

 mean velocity were then computed and plotted and the velocity curve 

 for the surface was drawn as described. It indicated that the axis 

 of the current lay closer to station 1082 than previously drawn but 

 its velocity of 48 centimeters per second differed only 4 centimeters 

 per second from the earlier determined value. 



