MIGRATION AND TEMPERATURE STRUCTURE 



OF EDDIES ON THE LEEWARD SIDE OF THE 



HAWAIIAN ISLANDS 



Edward L. Smith 

 U. S. Navy Electronics Laboratory 

 San Diego, California 



INTRODUCTION 



This paper discusses the variability of the oceanographic environ- 

 ment in the lee of the Hawaiian Islands caused by cyclonic and anti- 

 cyclonic eddies in their wake. The paper presents new data acquired 

 in the eddy region by means of the U. S. Navy Electronics Laboratory 

 Thermistor Chain. 



The chain was used during two cruises in the eddy region. Cruise 

 29 in August 1964, and Cruise 36 (made in conjunction with the Mar- 

 ine Physical Laboratory and based on the results of Cruise 29) in 

 July 1966. During Cruise 29 a cyclonic eddy 125 miles in diameter 

 was located. During Cruise 36, in the same region that had been 

 investigated in 1964, two smaller eddies were found. One was 

 cyclonic and near shore, the second was anticyclonic and west of the 

 first. In both studies two independent methods were used to define 

 the areas occupied by the respective vortices: internal temperature 

 structure as profiled by the thermistor chain, and relative currents 

 determined from ducted current meters attached to the chain. 



The data and results for each cruise are presented here separ- 

 ately. From the collective results some conclusions are drawn 

 with regard to the expected variation in environmental parameters 

 caused by the eddies. 



EQUIPMENT 



The internal temperature structure was plotted during both 

 cruises using the towed thermistor chain which provides a profile 

 of the temperature distribution to an average depth of 750 feet. 

 Thirty-four thermistors, spaced at 25-foot intervals along the chain, 

 sense the temperature, and their electrical output is transmitted to 

 the ship's laboratory. An analog computer determines the depth of 



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