mometers and to calculate thermometric depth, 

 density (crt), specific volume anomaly (O'Hagan, 

 1964), current velocity, and volume transport. 



During the Ice Patrol season dynamic heights, 

 temperature to 150 m., and current velocities 

 were transmitted to Commander, International 

 Ice Patrol at New York on a real-time basis. 

 These data were used to predict iceberg drift. 



Magnetic tapes from the Digital Data Logger 

 were reduced on a Control Data Corporation 

 3300 computer using a FORTRAN IV program 

 supplied by Bissett-Berman. This program lists 

 sample number, depth, temperature, salinity, 

 and sampling rate. 



Vertical profiles of oceanographic parameters 

 were plotted using the "HYDROGRAPH" pro- 

 gram developed at Coast Guard Oceanographic 

 Unit for an IBM 1130 computer. The vertical 

 profiles of temperature and salinity during the 

 Ice Patrol season are displayed in figures 38 

 through 56. The isopleths have been extrapo- 

 lated beyond the data field to the ocean-sediment 

 interface to facilitate calculation of dynamic 

 heights in shallow water. 



Dynamic Calculations in Shallow Water 



The calculation of dynamic heights in shallow 

 water was performed in a manner similar to 

 that of Helland-Hansen (1934). This method 

 assumes that the continental shelf between the 

 ocean-sediment interface and the reference sur- 

 face (1000 decibars in this case) is motionless 

 water. In other words, level isosteric surfaces 

 are assumed to extend horizontally shoreward 

 from the ocean-sediment interface of the con- 

 tinental slope. The details of this method are de- 

 scribed by Kollmeyer et al. (1967). 



Navigation 



Navigation was based primarily upon LORAN 

 A. The LORAN C receiver was inoperative 

 much of the time, and poor weather routinely 

 precluded celestial navigation. Dead reckoning 

 and bottom contours were also used. Some of 

 the station locations are known with an accu- 

 racy of only 5 to 10 nautical miles. 



DYNAMIC TOPOGRAPHY 



The dynamic topography of the sea surface 

 has traditionally been referred to the 1000 deci- 

 bar reference surface by the International Ice 



Patrol ; this practice was continued during the 

 1970 season. During the first cruise, observa- 

 tions were made only to depths slightly deeper 

 than 1000 m. to shorten station time and make 

 the survey as synoptic as possible. During the 

 second cruise, observations were made to 3000 

 m., depth permitting. 



Topography Relative to 1000 Decibars 



The normal (22-year mean) dynamic topog- 

 raphy of the sea surface for April (fig. 9) and 

 May (fig. 11) shows that the most prominent 

 feature of the circulation is the Labrador Cur- 

 rent flowing southward along the eastern slope 

 of the Grand Banks. Farther east, lying adja- 

 cent to the 1000 fathom curve, is the permanent 

 dynamic trough that separates the Labrador 

 Current from the northeastward flowing North 

 Atlantic Current. 



The dynamic topography from the first seg- 

 ment of the first cruise (fig. 7) agreed well with 

 the normal dynamic topography for April (fig. 



9) developed by Soule (1964). The dynamic 

 topography from the second and third segments 

 of the first cruise (fig. 8) also agreed with the 

 normal dynamic topography for April (fig. 9), 

 except for the indication of a dynamic low at 

 44N, 47W, offshore from the permanent dynamic 

 trough between the Labrador Current and the 

 North Atlantic Current. 



The first segment of the second cruise (fig. 



10) also showed a dynamic low at 44N, 47W. 

 Close comparison with the normal chart for May 

 (fig. 11) reveals that the dynamic heights in 

 this low were not abnormally low; rather, the 

 low was created by the presence of an unusual 

 dynamic high to the north at 45N, 46.5W. Dur- 

 ing the second segment of the second cruise 

 (fig. 12), there was a more intense dynamic 

 high at the same location. The temperature fea- 

 tures of this high extended to a depth of at least 

 1200 m. (fig. 53). Although the presence of a 

 high just south of Flemish Cap cannot be found 

 on the normal charts, it has been observed be- 

 fore. For example, a high was evident in the 

 dynamic topography of 17-25 May 1934, 10-20 

 April 1935, and 8-18 May 1935 as reported by 

 Smith et al. (1937). The high may have re- 

 sulted from the recurving of the North Atlantic 

 current. It is also possible that the highs ob- 

 served during the consecutive segments of the 

 cruise were not the same. 



