OCEANOGRAPHIC OBSERVATIONS 

 NORTH ATLANTIC OCEAN STATION DELTA 



27 AUGUST 1967-25 AUGUST 1968 



by 



ROBERT E. HAMMOND' 



INTRODUCTION 



Initial Coast Guard investigations on Ocean 

 Station DELTA (OS DELTA), located at 44°00'N, 

 41°00'W, began during a one month cruise in 

 April 1963 aboard the USCGC CASCO. Eighty 

 oceanographic stations were taken to determine 

 the spatial or temporal variations of temperature 

 and salinity in the upper 800 meters. McGary 

 and Morse (1964) concluded that the boundaries 

 of several distinct water masses occur near OS 

 DELTA and lead to large horizontal gradients 

 in temperature and salinity distribution. 



Experiments were conducted during five three- 

 week cruises by the U.S. Naval Oceanographic 

 Office (June 1962^uly 1963) to determine the 

 vertical and horizontal variability of water 

 properties in the immediate vicinity of OS 

 DELTA. Analyses of these data were presented 

 by Gorton (1967) in which the water masses at 

 OS DELTA were described as: (1) the surface 

 water mass of Gulf Stream origin which varies 

 in thickness from 475 meters to 800 meters, (2) 

 an intermediate water mass of cold water of 

 subarctic origin (with a small percentage of Medi- 

 terranean Water between 800 meters and 1000 

 meters) which extends to a depth of approximately 

 1750 meters, (3) a deep mass of North Atlantic 

 Deep Water between 1750 meters and 2750 

 meters, and (4) a bottom water mass below 2750 

 meters, distinctive of Newfoundland Basin Water 

 (2.3°-3.0°C, 34.90%o-34.96%o). 



The U.S. Coast Guard initiated a continuing 

 series of oceanographic observations at OS 

 DELTA in July 1966. Due to a limited number 

 of deep sea reversing thermometers, these obser- 

 vations were restricted to alternate three-week 



'U.S. Coast Guard Oceanographic Unit. Building 159-E. Navy Yard Annex, 

 Washington. DC. 20390. Presently with Commander. 17th Coast Guard District, 

 Juneau, Alaska. 



cruises during the first twelve months. Husby 

 (1969) reported on the data obtained from 136 

 oceanographic stations during the period from 

 July 1966 to August 1967; he pointed out signifi- 

 cant fluctuations in temperature and salinity 

 caused by changes in the North Atlantic Current 

 near OS DELTA. 



This report describes conditions based on 202 

 oceanographic stations at OS DELTA from 27 

 August 1967 to 25 August 1968. A summary of 

 oceanographic operations during that period is 

 presented in Table 1. Nansen casts were taken 

 daily during the occupation of OS DELTA unless 

 terminated by weather or other mission responsi- 

 bilities. In addition, casts using a salinity-tem- 

 perature-depth sensor system (STD) were con- 

 ducted on OS DELTA for the first time (6 July 

 to 9 July 1968) by USCGC HAMILTON. 



SAMPLING TECHNIQUES 



The location of OS DELTA in relation to the 

 other ocean stations of the world and Standard 

 Section A-3 is shown in figure 1. The bathymetry 

 in the vicinity of OS DELTA is shown in figure 

 2. 



Ocean station vessels attempt to maintain their 

 position within a ten mile square centered on 

 the ocean station, although extenuating circum- 

 stances occasionally prevent this. The station 

 position sheets (figs. 3-15) indicate those stations 

 occupied outside the ten mile square. 



The sampling program at OS DELTA consisted 

 of daily Nansen bottle casts to a depth of 1,500 

 m when weather and other operations permitted. 

 The desired sampling depths were surface, 25 m, 

 50 m, 75 m, 100 m, 150 m, 200 m, 300 m, 400 

 m, 500 m; 600 m, 800 m, 1,000 m, and 1,500 

 m. However, the first three cruises during the 

 period covered in this report did not sample at 



