TEMPERATURE OF THE SURFACE "WATERS OF THE ATLANTIC OCEAN 



lies for the Atlantic Ocean were obtained by taking 

 the differences between the average temperature of the 

 two-degree zones and the averages of the two-degree 

 field for each month and for the year. By interpolating 

 the two-degree field averages from the annual curve 

 of the five-degree averages, which Kriimmel ' indicates 

 for the combined oceans (Weltmeer), the annual 

 anomaly of the Atlantic Ocean compared with that of 

 the combined oceans for these two-degree zones was 

 derived. Finally, the two-degree field values also 

 served to ascertain the annual course of the tem- 

 perature. 



2. Temperature Distribution 



A survey of the distribution of the temperature on the 

 surface of the Atlantic Ocean (plate V) and for the 

 individual months (plates VI-XVII) will show that 

 the main features of the distribution coincide with those 

 found on earlier charts." In the south, extending in 

 front of the Antarctic Continent, is a large area with 

 low temperatures between 0° and — 1.5° C. North of 

 this area at about 50° S., there lies a zone which has a 

 sharp rise in temperature. The annual chart, drawn 

 according to the two-degree field values, shows this 

 sudden rise less clearly than the monthly charts based 

 upon one-degree field values. Tins zone of strong 

 temperature gradients extends to about 40° S. Farther 

 north, the rise in temperature takes place more slowly, 

 and at the same time the isotherms are oriented, not 

 approximately west-east, as on earlier charts, but 

 southwest-northeast. Special influences, such as the 

 Falkland Current, Agidhas Current, and plankton areas 

 in the various regions, which cause deviations from 

 these main features, will be discussed in a later section 

 of this report. The highest temperatures of 26° to 

 over 27° are reached in a zone which extends between 

 5° N. and 15° N. from the Gulf of Guinea to the Yucatdn 

 Sea. The absolute maximum of the annual average, 

 27.8°, hes in the two-degree field 80° W., 17° N. The 

 slightest temperature gradients appear in this warmest 

 zone of the ocean, which is enclosed on both sides by 

 the 26° isotherm, and which, like the meteorological 

 equator, extends northward of the geographical equator. 

 Over great stretches, the temperature of the annual 

 average in a north-south as well as in a west-east 

 direction changes by only a few tenths of a degree. 



In the middle latitudes of the northern hemisphere, 

 the temperature again decreases rather equably, and 

 the isotherms run in a northwest-southeast direction. 



• Kriimmel, Ilandbuch der OzeanograpMe. Bd. I, S. 401. Stuttgart, 1907. 



' G. Schott, Oeographie des Allantischen Ozeans, Hamburg, 1926. .attention is 

 also called to a work which appeared after the publication of the present discussion: 

 G. Slocum, The Normal Temperature Distribution of the Surface Water of the Western 

 North Atlantic Ocean. Monthly Weather Review, Vol. 6fi, No. 2., Washington, D. C, 

 February 1938; also Phil. E. Church, Temperatures of the Western North Atlantic 

 from Thermograph Records. Association d'Ocfanographie Physique, Union G^od. 

 et G6ophys. Internat. 1937, and G. Roux, Isothermes mensuelles procisoires de I'eau 

 de mer a la surface au targe des c6!es du Maroc. Annales de Physique du Globe de la 

 France d'outre-mer, 5. Jahrg. Nr. 25. Paris, 1938. 



This gradual decrease is suddenly interrupted on the 

 west side of the ocean from 35° N. to 40° N. by a zone of 

 sharp temperature increase; north of this area lies 

 one of uniformly low temperatures. It is the counter- 

 part of the antarctic cold water area, the so-called 

 "Cold Wall." As a result of the well-known effect 

 of the Gulf Stream and its offshoots, the eastern 

 half of the northern North Atlantic Ocean deviates 

 from this pattern. Here the relatively warm water, 

 which cools oft' gradually, advances far to the north and 

 displaces the transition zone between the cold arctic 

 water and the water south as far as the coast of Green- 

 land. 



This short survey of the temperature distribution is 

 supplemented by Appendix II, which contains the 

 zonal averages of the surface temperatures for zones of 

 two degrees of latitude for each month and for the year. 

 ^Vlien Ki-iimmel's * comparison of values for the Atlan- 

 tic Ocean and the combined oceans is studied (fig. 1),° 



vBO's ec 



' WS «r W 20* (T 2)- «r 60" «fH 



Figure 1. — Annual averages of surface temperature according 

 to two-degree zones for the Atlantic Ocean and according to 

 five-degree zones for the combined oceans. 



it becomes clear that the South Atlantic Ocean is colder 

 than the combined oceans up to a latitude of 40° S. 

 Between 40° S. and 25° S., a small excess of warmth is 

 produced, which does not, however, exceed 0.2° C. 

 The whole tropical zone as far as 20° N. exhibits con- 

 siderably lower temperature values than those cal- 

 culated for the whole ocean. The differential between 

 25° S. and 20° N. is not more than 2° C. From 20° N., 

 the North Atlantic Ocean shows a great excess of 

 warmth, which is ascribed both to the displacement of 

 the meteorological equator to the northern hemisphere 

 and to the Gulf Stream and its offshoots. This 

 excess increases up to about 3° C. In comparisons, 

 such as are made in Appendix II and table 1, the varying 

 density of the material observed in the oceans must 

 always be taken into consideration. When other 

 values are added, the position of the isotherms, 



' O. Kriimmel, Handbuch d. Ozeanographie. Bd. I, S. 401 Stuttgart, 1907. 

 ' The averages for two-degree zones are treated in Figure 1 and Table 1 as latitude 

 temperature in Kriimmel's sense of the term. 



