Appendix E 



An Analysis of Eddy Formation in tlie 

 Vicinity of the Grand Banlcs of 



Newfoundland 



LT F. J. Williams, USCG 

 D. L. Murphy 



Introduction 



The International Ice Patrol 

 conducted a study of the eddy 

 population in the 

 Newfoundland Basin region 

 based on data from the period 

 from November 1 981 to 

 December1984to 

 investigate the importance 

 and basic character of eddy 

 motion in the southern 

 portion (40°N-45°N and 

 40°W-55°W) of our patrol 

 area. This area (Figure E-1) 

 contains the confluence of 

 three surface currents and is 

 bathy metrically dominated 

 by the Grand Banks of 

 Newfoundland, the 

 Newfoundland Seamount 

 Range and the Newfoundland 

 Ridge. 



A similar study was 

 conducted by Voorheis, 

 Aagaard and Coachman in 

 1973. They researched 

 hydrographic data collected 

 during IIP cruises in an 

 attempt to establish an eddy 

 population. The present 

 study encompasses a larger 

 geographic area and also 

 introduces infrared (IR) 

 imagery. Voorheis, etal. 

 looked for eddies in 

 hydrographic data along 

 standard IIP transects. The 

 present study uses data 

 collection specifically 

 designed to locate eddies. 



Ocean frontal analysis charts 

 maintained by National 

 Weather Service (NWS) and 

 Naval Eastern Ooeanographic 

 Center (NEOC), and Canadian 

 Forces METOC Center sea 

 surface temperature data 

 fomied the data base for the 

 investigation. Analysts 

 produce these charts from 

 satellite IR imagery gathered 

 predominantly from the GOES 

 and NOAA 6 and 9 satellites. 

 The research area is 

 dominated by cloud and fog 

 cover and so does not always 

 present ideal conditions for 

 use of IR imagery, but these 

 charts represent the only 

 complete data set displaying 

 eddies. An explanation of the 

 methodology is given in 

 Williams (1985). Data 

 analyzed include the number 

 of eddies in the area, their 

 average life span and size, 

 the area of formation, 

 generation and deterioration 

 patterns, and their movement 

 through the area. Eddies 

 included in the study are only 

 those in the southern portion 

 of the area that had an IR 

 signature. Other eddies may 

 affect the operations area, 

 but are not included. 



Eddy Population 



Eighty-five percent of the 

 time at least one eddy was 

 active in the research area, 

 and on several occasions two 

 or more were present. During 

 the 38 months of the 

 experiment the NWS and NEOC 

 charts indicated 46 eddies in 

 the area. The life of the 

 eddies ranged from two to 

 218 days with an average 

 life span of 42 days. 

 Voorheis, era/. (1973), 

 indicates an average life 

 span of 30 to 120 days. 



Areas of Formation 



The positions of fonmation of 

 the eddies as shown in Figure 

 E-2 indicate that they 

 formed in two major areas: 

 over the Newfoundland Ridge 

 and over the Newfoundland 

 Seamount Range. Of the 46 

 observed eddies, 12 (26%) 

 were first sighted directly 

 over the Newfoundland 

 Seanrxxjnt Range and 34 (74%) 

 were first sighted west of 

 the Newfoundland Ridge. 

 These areas are both 

 dominated by large, 

 relatively shallow 

 bathymetric features. 

 Huppert and Bryan (1 976) 

 have demonstrated that the 

 Atlantis II Seamounts are 

 instrumental to eddy 



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