Discussion of Vertical Property Distribution 

 and Dynamic Heights 



INTRODUCTION 



There has been an increasing awareness of 

 the inadequacy of the assumption of steady 

 state conditions in describing the features of 

 the ocean as the vokime of data has increased. 

 The development of valid dynamic models re- 

 quired that the temporal and spatial changes 

 in the feature or area being investigated be 

 taken into account. Once a significant time 

 rate of change of oceanic parameters is deter- 

 mined, the variations must be examined and 

 some account of them taken in the sampling 

 program. To do this, monitoring sections v^^ere 

 established to determine the annual variations 

 in the Labrador Current. These sections were 

 also chosen to provide Commander, Interna- 

 tional Ice Patrol with real-time information 

 about the oceanographic conditions on the 

 Grand Banks. 



Data obtained from a complete occupation 

 of the three Standard Sections were used to 

 determine the difference between the observed 

 dynamic topography and the monthly mean 

 dynamic topography. The calibrated monthly 

 mean charts were then used to predict future 

 iceberg positions. Monthly occupation of these 

 sections will permit a complete description of 

 the annual oceanographic conditions of the 

 Grand Banks region. A complete oceano- 

 graphic description should provide the 

 following information about the pertinent 

 parameters : 



1. Their arithmetic means 



2. Their seasonal and annual variations 



3. Their extremes 



4. The rate and frequency with which the 

 variations occur. 



Smith (1937) was the first to recognize the 

 importance of short term variability in the 

 Labrador Current when he stated, "The 



Labrador Current is also marked by frequent 

 irregular pulsations occurring within the in- 

 terval of a few weeks or of a month or two. . . 

 that an iceberg observed drifting southward 

 at a moderate rate may suddenly accelerate to 

 double or sometimes triple its former rate." 

 He further indicated that this acceleration was 

 due to a local contraction in the width of the 

 current and not an acceleration along the en- 

 tire length of the current. Soule and Graves 

 (1938) indicated that the volume transport of 

 the Labrador Current varied significantly over 

 a three month interval. Montgomery (1938) 

 and Iselin (1940) showed that there were 

 variations in the net volume transport of the 

 Gulf Stream. Fuglister (1951) indicated that 

 the volume transport of the Gulf Stream varied 

 monthly. Sverdrup, Johnson, and Fleming 

 (1942) discussed the simultaneity of oceano- 

 graphic observations and the .steadiness of the 

 flow. They stated that in the interval of time 

 between surveys the details of the relative 

 topography may have changed greatly, but the 

 main features have changed more slowly. 

 Fuglister and Worthington (1951) implied 

 that synopticity was an important enough con- 

 sideration to require multiple ship surveys. 

 Worthington (1954) showed that a significant 

 change in the direction of the Gulf Stream 

 occurred within four days. Dinsmore, Morse, 

 and Soule (1960) found that the dynamic 

 topography had changed within the approxi- 

 mately three-day interval between the occupa- 

 tion of two sections of an interrupted survey. 

 Bullard et al. (1961) indicated that the volume 

 transport through sections U, W, and T 

 changed significantly with time. 



Kollmeyer et al. (1965) revised the track- 

 lines used by the International Ice Patrol in 

 the southern part of the Grand Banks. These 

 changes permitted the surveys to be completed 



5 



