This T-S curve will henceforth be referred to as 

 Iselin's North Atlantic Central water T-S curve. 

 To determine if North Atlantic Central water 

 occurred at OS DELTA, plots were made of a 

 typical T-S curve from each cruise along with 

 Iselin's T-S curve (fig. 3). Although there are 

 variations from his T-S curve it is obvious from 

 this figure and from all the T-S curves on OS 

 DELTA (figures 4 to 16) that OS DELTA was 

 dominated by North Atlantic Central water. 



North Atlantic Current 



Iselin (1936) describes the North Atlantic 

 Current as an extension of the Gulf Stream to 

 the eastward of the Tail of the Banks. At pres- 

 ent there is considerable conjecture as to the 

 path of the North Atlantic Current east of the 

 Grand Banks. 



Fuglister (1951) believes that the Gulf Stream 

 consists of multiple currents and counter cur- 

 rents as far west as 65° west longitude (fig. 17). 

 OS DELTA appears to be right in the middle 

 of this flow. Whether or not this is true can be 

 at least partially determined from a considera- 

 tion of the T-S curves on OS DELTA. 



The T-S curves for 15 January to 4 May 1969, 

 cruises D29 to D32, are typical of North Atlantic 

 Central water (figs. 9 to 12). The T-S curves 

 for the rest of the year from 26 August 1968 to 

 9 January 1969, cruises D23 to D28, (figs. 4 to 

 8) and 29 May to 26 August 1969, cruises D34 

 to D37, (figs. 13 to 16), are also typical of North 

 Atlantic Central water but have distinct differ- 

 ences from the first group (15 January to 4 May 

 1969). 



In the first group of T-S curves the tempera- 

 ture rarely reached 15°C and the salinity rarely 

 exceeded 36.0 °/oo- The salinity maximum for 

 the first group was always at the surface. For 

 the second group of T-S curves the temperature 

 was always 15°C or greater and the salinity al- 

 most always exceeded 36.0°/oo- The salinity 

 maximum, for the second group, for the most 

 part, was a subsurface maximum. The surface 

 salinities were considerably lower than the sub- 

 surface maximum for the second group. 



The first group of T-S curves did not indicate 

 North Atlantic Current. The second group did 

 indicate the presence of the North Atlantic Cur- 

 rent. Rigorous proof of this is beyond the scope 

 and the purpose of this report and will not be 



considered here. However this discussion shall 

 briefly touch upon the significance of the differ- 

 ences between the two groups of T-S curves. 



First of all, Fuglister and Voorhis (1965) used 

 the 15°C isotherm at 200 meters as an indicator 

 of the left hand edge of the Gulf Stream (North 

 Atlantic Current). Therefore, if there were no 

 15°C temperatures it is possible there was no 

 North Atlantic Current. Secondly, only when 

 there were 15°C temperatures did the salinity 

 exceed 36.0°/oo, except in a few instances. 

 Thirdly, the low salinities at the surface mean 

 that the subsurface salinity maximum could not 

 have been caused by evaporative processes. 

 Finally, Neumann and Pierson (1966) believe 

 that the Labrador Current injects salinities into 

 the North Atlantic Current which then trans- 

 ports these salinities across the North Atlantic. 

 Only when 15°C temperatures were present was 

 there any low surface salinities. It appears that 

 these low surface salinities were transported by 

 the North Atlantic Current. 



Reiterating, the North Atlantic Current was 

 present on OS DELTA only when temperatures 

 were 15°C or greater, when salinities exceeded 

 36.0°/oo and when the surface salinities were 

 lower than the salinity maximum. These three 

 factors are the three main differences between 

 the first group of T-S curves and the second 

 group. Hence it is logical to assume that the 

 first group of T-S curves from 15 January to 

 4 May 1969 did not indicate the North Atlantic 

 Current and the second group of- T-S curves 

 from 26 August 1968 to 9 January 1969 and 29 

 May to 26 August 1969 did indicate the presence 

 of the North Atlantic Current. 



Subarctic Intermediate Water 



Waters of Subarctic Intermediate origin can 

 be distinguished by applying the salinity anom- 

 aly method of Helland-Hansen and Nansen 

 (1926) using Iselin's North Atlantic Central 

 water T-S curve (fig. 3) as a standard. Bubnov 

 (1968) gives a temperature range for Subarctic 

 Intermediate water of 4.5°C to 7.0°C and a 

 salinity range of 34.70%o to 35.00°/oo in his 

 southern area of formation (near Ocean Station 

 CHARLIE, Hannon, 1973). Since Subarctic 

 Intermediate water is lower in salinity than 

 North Atlantic Central water, water of subarctic 

 origin will have a negative salinity anomaly. 

 For example, a —20 salinity anomaly means that 



