UPDATING THE NORMAL DYNAMIC TOPOGRAPHY CHARTS 



Background 



Floyd M. Soule, who was a prominent member 

 of International Ice Patrol for a period span- 

 ning more than 30 years, published the original 

 normal dynamic topography charts of the Grand 

 Banks area (Soule, 1964). These charts were 

 developed primarily for use by Commander, 

 International Ice Patrol (CUP). Before ex- 

 plaining how they were updated, the evolution 

 and use of these charts will be reviewed. 



The 15 April 1912 sinking of the luxury liner 

 Titanic following her collision with an iceberg at 

 41°16'X, 50°14'W, some 300 miles south of New- 

 foundland, prompted international shipping in- 

 terests to demand that an organization be fomied 

 to continually advise the mariner of the iceberg 

 danger. The result of this outcry was the estab- 

 lishment of the International Ice Patrol by the 

 International Convention for the Safety of Life 

 At Sea (SOLAS) in 1913. This service, financed 

 by SOLAS member nations and operated by the 

 U.S. Coast Guard, is designed to advise the 

 mariner of any iceberg danger, as well as to 

 conduct oceanographic research, in the area of 

 the Grand Banks. The oceanographic conditions 

 in this area are very complex as it is the conflu- 

 ence region of the cold southerly flowing Labra- 

 dor Current and the warm northerly flowing 

 North Atlantic Current. 



During the first few years of Ice Patrol, the 

 emphasis was placed on ice observation and ad- 

 visories. As a result, the oceanographic data 

 collected was quite sparse and of only limited 

 value. However, as oceanographic techniques 

 and equipment improved, it became apparent 

 that oceanographic operations could be valuable 

 to CUP. For the first time in 1931 an Ice Patrol 

 vessel was devoted to oceanographic research, 

 and by 1934 data were being collected in a sys- 

 tematic and concentrated manner. 



That year, two significant changes in IIP op- 

 erations occurred. First the Wenner Salinity 

 Bridge replaced the tedious titration method 



previously used to determine salinity. This 

 greatly improved the accuracy and ease with 

 which salinity samples could be determined 

 (Soule and Hoyle, 1935). This instrument was 

 used exclusively through the 1961 ice season. 

 Then after two years of comparative testing, it 

 was phased out and replaced by commercially 

 produced poi'table inductive salinometers. The 

 second change in 1934 was the replacement of the 

 .lacobsen and Jensen method of determining 

 dynamic heights in shallow water with the 

 Helland-IIansen method (Soule and Hoyle, 

 1935). This method is still used, although it has 

 been slightly modified for adaption to computer 

 usage (Kollmeyer, et al., 1967). 



Since 1934 only one other major change in the 

 collection and processing of data has been made. 

 In 1966, the STD replaced the Nansen bottle as 

 the. primary sampling device. However, Nansen 

 bottles equipped with deep sea reversing ther- 

 mometers continue to be used to quality control 

 STD data. 



Use 



Every year that IIP has been conducted since 

 1934, at least some time has been spent surveying 

 the northeastern, eastern, and southern slopes of 

 the Grand Banks. As the general oceanic cir- 

 culation in this area is similar from year to year, 

 Soule felt that monthly normal dynamic topog- 

 raphy charts would be of use to CUP. They 

 definitely have been. At times during the peak 

 of the ice season (April- July), when no data are 

 being collected, CUP utilizes the normal charts 

 as an aid in predicting iceberg drift. 



Update 



Soule's normal charts were based on 22 years 

 of data collected from 1934-1941 and 1949-1961; 

 IIP was suspended during World War II. For 

 this first revision of the normal chaits, data from 

 1962 tlirough 1972 were added to the original 

 data base. The data used in this revision con- 

 sist of 



