for the Arctic Bottom Water at a given depth to be colder during 



the BELGICA cruise and during the cruise of H.M.S. FARM in 1910 (Helland- 



Hansen and Nansen 1912) . These temperature differences could be 



a reflection of climatic changes, but further study is necessary 



to verify this. 



Minimum Arctic Bottom Water temperatures found during a recent 

 summer survey were approximately -1.10°C (Gladfelter 1964) and were 

 encountered in the 'core' of the Arctic Bottom Water formed in the 

 Greenland Gyre. Gladfelter has shown that the center of this formation 

 lies at approximately 75°N and 0°, and this probably explains why 

 the coldest bottom water temperatures were found in the more southerly 

 portions of the EDISTO survey region (Figs. 11, 23, and 25). 



Metcalf (1960) states that a major cause of the increase in bottom 

 water temperatures as one travels into the northern Greenland Sea 

 is the penetration of the warmer bottom water formed in the Norwegian 

 Gyre (see Section IV). According to him, this water appears to travel 

 north under the West Spitsbergen Current and eventually takes a position 

 around the colder Arctic Bottom Water formed in the Greenland Gyre. 

 He suggests that the volume of bottom water formed in the Norwegian 

 Gyre is greater than that formed in the Greenland Gyre and that 

 the colder water formed in the Greenland Gyre gradually loses its 

 characteristics through mixing with warmer water from the Norwegian 

 Gyre. Although this hypothesis is not unreasonable, it would seem 

 that mixing of the bottom water formed in the Greenland Gyre with 

 other warmer waters found in the region could also produce the observed 

 temperature distribution. For example, if one examines the temperature 

 and salinity distributions at 500 meters (Figs. 21 and 22), it becomes 

 clear that in many cases water with temperatures warmer than 0°C 

 and salinities almost the same as those in the Arctic Bottom Water 

 was present. Moreover, there is evidence that the coldest Greenland 

 Gyre Arctic Bottom Water has salinities which are slightly lower 

 (*=« 34.88 % instead of « 34.91 %„) than Arctic Bottom Water with 

 slightly higher temperatures (Helland-Hansen and Nansen 1912, Gladfelter 

 1964). Thus, even if one took a rather extreme case and mixed Greenland 

 Sea Gyre Arctic Bottom Water with a temperature of -1.15°C and a 

 salinity of 34.88 % n with Atlantic Water of 35.05 % and 4°C in proportions 

 of 9 to 1, the resulting water would have a temperature of -0.63°C 

 and a salinity of 34.90 % . These characteristics fall well within 

 the definition given for Arctic Bottom Water, but the mixture is 

 now so warm that it could be mistaken for Arctic Bottom Water from 

 the Norwegian Gyre. Therefore, it would appear that more study is 

 necessary before the manner in which the coldest Arctic Bottom Water 

 becomes warmer can clearly be defined, and before one definitely 

 can assert in which of the two great gyres, the Norwegian or the 

 Greenland, does the bulk of the Arctic Bottom Water originate. Certainly, 

 mixing with waters other than bottom water from the Norwegian Gyre 

 cannot be neglected when considering the processes which raise the 

 temperatures of the colder bottom waters from the Greenland Cyre. 



36 



