144 The Three-dimensional Temperature Distribution and its Variation in Time 



32 



24 



u 



° 20 



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^ 16 



o 

 i> 



Q. 



E 



I 



2° 



200 400 600 800 1000 1200 



Sea miles towards SE 



Fig. 60. Surface temperature distribution in the western North Atlantic (in the area of the 

 Gulf Stream) from repeated temperature recordings made along shipping routes (according 



to Church). 



In the western part of the North Pacific there is also a similar phenomenon at the 

 boundary between the warm Kuroshio and the cold Oyashio where arctic water and 

 subtropical water come advectively in close contact. 



Due to the lack of data it was for a long time impossible to determine the position 

 of this discontinuity in the circumpolar water in the Southern Hemisphere. Meinardus 

 (1923) first showed its presence from observations made in the southern Indian Ocean. 

 Its position in the Atlantic was deduced later from the current charts and it was 

 recognized as the line of covergence between the oceanic west wind drift and the Ant- 

 arctic water (Defant, 1928). It runs from about 48° W. to well out into the Indian 

 Ocean (80° E.) between latitudes of 50° and 48° S. and then gradually turns south- 

 wards to about 62° S. at Drake's Passage. 



(4) A second temperature discontinuity which is sometimes more sharply marked, 

 though it can still only be detected on continuous recordings, lies where the sub- 

 tropical water meets the subarctic water of the oceanic west wind drift {subtropical 

 convergence). The frontal discontinuity in the region of the subtropical convergence 

 shows large local meridional displacements and is therefore completely smoothed in 

 mean temperature charts. Figure 61 shows two thermograph recordings given by 

 Deacon (1938) that were taken on passing through the subtropical convergence and the 

 Antarctic convergence {oceanic polar front). They show clearly the character of frontal 

 discontinuity of this dynamically important phenomenon. 



(5) A useful aid in comparing temperature conditions in the oceans, especially in 

 a zonal direction, are charts with lines of equal deviation from the normal value charac- 

 teristic for each latitude. Such isoanomalic charts show which parts of the ocean are 

 cold and which are warm relative to a normal latitude. In the Atlantic the heat surplus 

 from the Gulf of Mexico across the North Atlantic to the Norwegian Sea as far as 



