bottom was substituted for one of the 1500 meter 

 casts. The desired sampling depths were 0, 25, 

 50, 100, 150, 200, 250, 300, 400, 500, 600, 800, 1000, 

 1500, for the shallow casts and 2000, 2500, 3000, 

 and 150 and 50 meters off the bottom for the 

 deep casts. 



The sampling program for the S/T/D En- 

 vironmental Profiling System (STD) equipped 

 vessels consisted of four STD casts per day to 

 1500 meters. Once a week a 3000 meter STD 

 cast was substituted for one of the 1500 niet«r 

 casts. 



The processing of the Nansen and STD data 

 has been thoroughly covered by Rosebrook 

 (1971) and will not be discussed here. 



ANALYSIS OF DATA 



Introduction 



OS DELTA is influenced by several water 

 masses and by the North Atlantic Current. The 

 names of the water masses of OS DELTA along 

 with their characteristics and the source of these 

 definitions are given in Table 2. 



Table 2. Water masses found on Ocean Station DELTA, 

 Water Mass 



North Atlantic Central water 



Subarctic Intermediate water 



Mediterranean water 



Labrador Sea water 



Labrador Sea water (LS) 

 mixed with North East 

 Atlantic Deep water 

 (NEAD) [on OS DELTA) 



North Atlantic Deep water 



Characteristics 



T°C S°/oo 



4.0 and 3S.0 



to 



18.0 and 36.6 



4.5 34.70 



to to 



7.0 35.00 



2.0 and 34.8 

 to 



12.0 and 36.5 



3.4 34.9 



August 1968 to August 1969 



Depth [m) 

 on OS DELTA 



to 1500 



Source 



500 to 1500 



700 to 1100 



1500 to 2000 



2000 to 3200 



3200 to 4600 



Iselin's Sargasso Sea 

 T-S curve (1936) 



Bubnov (1968) 



Defant's T-S curve 

 (1961) 



Northington and Metcalf 

 (1961) 



LS + NEAD, Hannon (this 

 paper). NEAD, defined 

 by Worthington and 

 Metcalf (1961) , named 

 by Lee and Ellett (1967) 



Worthington and Metcalf 

 (1961) and Wright and 

 Worthington (1970) 



North Atlantic Central Water 



North Atlantic Central water is formed, as the 

 name implies, in the central North Atlantic 

 (Iselin, 1939). OS DELTA is on the north- 

 eastern edge of the proposed area of formation 

 of North Atlantic Central w^ter (fig. 2). Ac- 

 cording to Iselin, this water probably attained 

 its characteristics while in contact with the at- 

 mosphere. By using sea surface temperature- 

 salinity charts from an atlas (Bohnecke, 1936), 

 Iselin plotted temperature-salinity values from 

 the surface together with typical vertical T-S 

 curves in th« mid-Atlantic Ocean. These sur- 

 face values which represent a horizontal T-S 

 curve nearly coincided with the vertical T-S 



curves. Other surface values could be chosen to 

 obtain complete coincidence. This result sup- 

 ports the generally accepted hypothesis that 

 North Atlantic Central water is formed by the 

 sinking of surface waters and by lateral mixing. 

 The variations in a vertical T-S curve could be 

 due to the different temperatures and salinities 

 of the surface waters from different areas of the 

 Atlantic. Since these surface waters have the 

 same density, they sink and form North Atlantic 

 Central water. This does not rule out vertical 

 mixing but it would appear that it is not the 

 main contributor to this water's formation. 



Iselin's T-S Sargasso Sea curve (1936) is rep- 

 resentative of North Atlantic Central water. 



