140 MARION AND GENERAL GREENE EXPEDITIONS 



Avhich, as might be expected near the turning point of a discharge, 

 are greater than farther upstream in the trunk. The volume of the 

 Atlantic Current according to the table also shows considerable varia- 

 tion, but this of course is due to the position of the stations, some 

 sections extending deeper into the margin of the warm, salty stream 

 than others. The values are recorded in order to demonstrate that 

 the Grand Banks sections in most cases intersect the Atlantic Cur- 

 rent itself and not a secondary tongue or eddy. 



ANNUAL CYCLE 



The bulk of the subsurface observations that have been made in 

 the Grand Banks sector have occurred in spring and summer. A few 

 stations, however, have been taken by the ice observation cutter dur- 

 ing winter (Smith, 1922, 1923). The United States Coast Guard 

 also made a brief physical survey of the waters around the Grand 

 Banks in October 1923 (Smith, 1923). The Challenger ran a line of 

 stations across the Grand Banks in November 1932 (Conseil Per- 

 manent International, 1933), and the Atlantis a line of stations south 

 of the Tail of the Grand Banks in September 1935 (Conseil Perma- 

 nent International, 1936) . These data, although scanty for the colder 

 months of the year, provide a basis, however, for describing the annual 

 cycle. 



The only two winter surface temperature maps of the Grand Banks 

 sector, February 19-March 11, 1921, and February 19-20, 1922 (Smith, 

 1922 and 1923), record temperatures less than 32° F., and thus indi- 

 cate that the Labrador Current at the time extended southward along 

 the east side of the Grand Banks to the vicinity of the Tail. In fact, 

 the isotherms on the two above maps, when due allowance is made 

 for the annual cycle of insolation, correspond in their main features 

 to those on the maps of the Ice Patrol's large collection for spring 

 and summer. Corroboration that the Labrador Current was present 

 in the Grand Banks sector in the winter of 1922 is found in the 

 computed volume of the cold current, between stations 172 and 173 

 (Smith, 1923, p. 70) of 6.2 million cubic meters per second. This 

 figure based upon only two stations is believed somewhat inaccurate, 

 since it is about double the average volumes previously found. 



The dynamic topographic map for October 21-26, 1923 (fig. 105), 

 when compared with the distribution of temperature and salinity 

 (Smith, 1923) , clearly shows that the Labrador Current with negative 

 temperatures in its axis flowed southward in autumn around the 

 Grand Banks to slightly west of the Tail. The computed volume of 

 the cold current was 3.4 million cubic meters per second near the 

 forty-fourth parallel and 2.9 million cubic meters per second at the 

 Tail, discharges which according to the table (p. 143) agree with the 

 volumes of the Labrador Current at other times of the year. The 

 computed volume of the cold current at the Tail of the Grand Banks 

 from observations in November 1932 and also in September 1935 tend 

 to corroborate the foregoing. ^^ 



Reference has already been made (p. 63) to the strength of the 

 West Greenland Current as found by the Meteor around Cape Fare- 

 well the winter of 1935 and also to the major proportions of the West 



"Smith fl924, p. 65) reported the drift of an iceberg southward around the Tail of the 

 Grand BanlfS in August and September 1923. 



