OCEANOGRAPHIC CONDITIONS, 1972 



A. D. ROSEBROOK 



(U.S. Coast Guard Oceanographlc Unit) 



Three oceanographlc cruises during the period 3-23 April, 5-22 May, 

 and 3-22 June 1972 were conducted In support of the International Ice 

 Patrol aboard USCGC EVERGREEN (WAGO-295) . Salinity and temperature data 

 were collected to a depth of at least 1000 meters using a Sallnlty- 

 Temperature-Depth (STD) Sensor System. Data were recorded on magnetic 

 tape using a digital data logger further processing upon return to the 

 C.G. Oceanographlc Unit. From these processed data, charts of dynamic 

 topography of the sea surface relative to the 1000 declbar level of no assumed 

 motion were constructed (figures 24-26) . The dynamic topography charts 

 show several prominent features of the general circulation pattern on 

 the Grand Banks. The Labrador Current can be seen flowing southward 

 along the eastern slope of the Grand Banks near the 1000 meter depth 

 contour. Located to the east is a dynamic trough separating the colder 

 Labrador Current waters from the northward flowing North Atlantic Current 

 water. Water from the dynamic trough is characterized by its low 

 specific volume resulting from mixing between the two currents 



The dynamic topography charts of the Grand Banks region from the 

 three surveys agreed well with the normal or average dynamic topography 

 for the months of April, May, and June. There was evidence of an 

 additional dynamic low in the vicinity of 4A°N, 47"'W during the April 

 survey (figure 24). During the May survey, a poorly defined dynamic 

 low was observed farther to the east near 44"*N, AS'W (figure 25). The 

 modified survey taken during June did not extend far enough to the east 

 to determine if a dynamic low was still present during this period. 

 During the period 7-15 June, EVERGREEN was assigned as Surface Patrol 

 Vessel and stood by a large tabular iceberg (mass approximately 3 x 

 10 kgs.) located near 42.5°N, 49.5''W. While standing by the Iceberg, 

 EVERGREEN occupied a series of 12 oceanographlc stations around the 

 berg. As a result, a total of 28 stations was taken in a rather small 

 area during the survey. The resulting dynamic topography of this 

 region is much more complex than that found in the remainder of the 

 survey area (figure 26) . 



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