Oceanographic Observations Between Iceland and 

 Scotland, July-November 1965 



INTRODUCTION 



In October 1965 the Coast Guard Oceano- 

 graphic Unit initiated an oceanographic pro- 

 gram to study the interchange between the 

 North Atlantic Ocean and northern adjacent 

 seas. This was a logical extension of the Coast 

 Guard Oceanographic Unit program of syste- 

 matic time-series studies at ocean stations 

 BRAVO, CHARLIE, DELTA, and ECHO and 

 the standard section program to obtain data en 

 route to these stations. The initial cruises were 

 planned to obtain measurements of the inter- 

 change through sections connecting southern 

 Greenland, Iceland, and Scotland. Relatively 

 short-term variations, on the order of a week 

 to a month in duration, were of interest, as well 

 as seasonal or longer variations which were to 

 be determined by seasonal reoccupation of the 

 sections. 



As pointed out by Steele, Barrett, and Worth- 

 ington (1962), a number of investigations have 

 shown that conditions along the Iceland-Faroe 

 Ridge are quite variable. One of the most com- 

 prehensive studies of the interchange between 

 the Norwegian Sea and the North Atlantic 

 Ocean through the Iceland-Scotland area was 

 presented by Tait and Martin (1957 and 1961). 

 Approximately 80 sections taken between 1927 

 and 1958 were presented in the two publications. 

 The volume transport through sections between 

 Faroe Bank and Butt of Lewis were compared 

 to volume transports through sections between 

 the Faroe and Shetland Islands. The volume 

 transports computed from data taken quasi- 

 synoptically at the two sections were generally 

 in good agreement ; however, they changed con- 

 siderably from survey to survey. Further evi- 

 dence of the variability of the interchange is 

 given by Cooper (1955). Steele, Barrett, and 

 Worthington (1962) pointed out the possibility 

 that the assumptions of no vertical motion re- 

 quired for geostrophic flow might not hold in 

 this area due to vertical mixing near the edge 

 and components of motion down the ridge. They 

 hypothesized that a better study of velocity, 

 volume transport, and water mass character- 

 istics could be made just south of the Ridge. 



Subsequently, they conducted a two-ship survey 

 in the area south of Iceland and off the Ridge to 

 investigate whether calculated and observed 

 currents were in agreement. Analysis of the 

 data indicated that there was close agreement 

 between the direct current measurements made 

 using neutrally buoyant floats and those cal- 

 culated from routine hydrographic observations. 

 Based on the work cited above, the Coast 

 Guard Oceanographic Unit initiated its study 

 of the interchange between the Norwegian Sea 

 and the North Atlantic Ocean by occupying a 

 section approximately parallel to, but southwest 

 of, the Iceland-Faroe Ridge (fig. 1). This sec- 

 tion was occupied once in July 1965 by USCGC 

 NORTHWIND (WAGB 282) and four times in 

 a 27-day period in October and November 1965 

 by USCGC EVERGREEN (WAGO 295). Data 

 from both cruises are included in Appendix 1, 

 which also includes data obtained between 

 Greenland and Iceland during the same cruises 

 but not discussed in this report. 



DATA COLLECTION PROCEDURE 



Oceanographic data were obtained at approxi- 

 mately 35-mile intervals along the sections il- 

 lustrated in figure 1 using an electronic bathy- 

 thermograph and teflon-lined Nansen bottles. 

 Desired sampling depths were 0, 10, 25, 50, 100, 

 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1250, 

 1500, 2000, and 2500 meters insofar as depth 

 of water permitted. In addition, an attempt was 

 made to obtain samples at 25 and 100 meters 

 above the bottom. The standard depths were 

 frequently modified to define better the vertical 

 temperature distribution as described by the 

 electronic bathythermograph trace. 



When the water depth exceeded approximate- 

 ly 1000 meters, two casts were made in order to 

 limit the load on the hydrographic wire. Gen- 

 erally the upper 1000 meters were sampled on 

 one cast and the layer from somewhat above 

 1000 meters to the bottom on the other. The 

 casts were overlapped for purposes of quality 

 control. On deep casts aboard USCGC EVER- 

 GREEN (WAGO 295) a 12-kc pinger was used 

 in conjunction with a precision echo sounding 



