14 



TEMPERATITRE OF THE SURFACE WATERS OF THE ATLANTIC OCEAN 



O. H. Felber ^^ show, the dynamic boundary runs 

 between these types of water (fig. 16). 



Like the subtropical boundary and subtropical con- 

 vergence in the boundary area between the Falkland and 



Figure 15. — Surface currents and temperature distribution in 

 the area of the Falkland and Brazil currents in February. 

 Designation of the fronts is the same as in figure 4. 



Bra?il Currents, polar front and subtropical boundary 

 coincide. This coincidence is characteristic of the area 

 off the east coast of North America to about 45° W. 

 At this longitude, the isotherms begin to radiate in the 

 form of a fan from southeast to northeast. 



Table 6. — Average position of the fronts and boundaries and 

 average temperatures in the North Atlantic Ocean at 30° W. 

 long. 



Parentheses indicate that the data have not been well estab- 

 lished. 



M. van Kiel, Surface Temperature in the Northwestern Part of the Atlantic 

 Kon. Nederl. Met. Inst. Nr. 102. Medd. en Verb. Nr. 35. 's Gravenhage, 



" P. 

 Ocean. 

 1933. 



See also O. H. Felber, 

 zwischen 16" und 60° N. Br. 



Oberfidchenstrdmungen des Nordatlantischen Ozeans 

 Archiv d. Seewarte. Bd. 53, Nr. 1. Hamburg, 1934. 



In order to establish whether boundaries such as those 

 which are found in the south are also present in the 

 eastern half of the North Atlantic, and if so, where they 

 are to be found, the meridional course of the tempera- 

 ture and of the gradients along 50° W., 30° W., and 

 12° E. was investigated according to the method pre- 

 viously indicated. The results showed that three 

 boundaries are apparent through rather large tempera- 

 ture gradients; of the three boundaries, however, the 

 two southern ones could be recognized only up to about 

 38° W. (table 6). At 46° W., 45° N., the polar front 

 leaves the hitherto common front in a northerly direc- 

 tion, turns east at 55° N., and moves in an S-shaped 

 curve through the Irminger Sea as far as the coast of 

 east Greenland. Here it runs along at a short distance 

 from the coast and approximately parallel to it, crosses 

 the Denmark Straits, and can still be detected east of 

 Iceland, where the East Iceland polar current meets 

 the ofTshoot of the Gulf Stream. Insofar as can be 

 determined from the scanty observations in winter, 

 one polar front follows this course (A„) approximately 

 in the months November to March. In the summer 

 near Cape Farewell this polar front turns into Davis 

 Strait, crosses it, and goes parallel to the Labrador coast 

 southward, and ends at about 50° N. on the coast of 

 Newfoundland (As). The seasonal changes of position, 

 caused by climatic influences, are thus rather great. 

 These changes become understandable when the funda- 

 mental difference between the southern and northern 

 hemispheres are considered. In contrast to the great 

 water areas in the south, in the north there are only small 

 sea spaces, often interrupted by land masses. In addi- 

 tion, these waters are penetrated and warmed by the 

 Gulf Stream system and its offshoots. While the areas 

 in the south comparable to the Irminger Sea and south- 

 ern Davis Strait have an almost permanently polar char- 

 acter, in the north a pronounced seasonal course can be 

 developed. The recession of tlie ice masses during the 

 summer melting period, combined with the warmth, 

 leads to the formation of a warm, though thin, top 

 layer. The cold polar water masses accordingly 

 disappear from the open ocean and, along with the 

 polar front, become merely a narrow belt on the coast 

 of Greenland and Labrador. Details of the course of 

 the front cannot be shown on the monthly charts. 

 Nevertheless the fishery patrols by the Meteor in 

 1929-30 provided an opportunity for studying the pro- 

 cesses at the polar front during the summer. Figure 

 17 shows the probable average water movement in the 

 summer (August), drawn up by A. Defant ^' on the 

 basis of the distribution of temperature, saline content, 



" G. Biihnecke, Hentschel. und Wattenberg, Cber die hydrographischen, chemischen 

 und biologischen Verhdltnisse an der Meeresoberfldche zwischen Island und QrSnland. 

 Ann. d. Hydr. LVIH. Berlin, 1930. 



See also G. Bbhnecke, Beitrdge Zur Ozeanographie des Oberflachenwassers in der 

 Daiiemark-Strasse und Irminger See. Ann. d. Hydr. LIX. Berlin. 1931 and A. Defant, 

 Bericht uber die Ozeanograph. Untersuchungen des Vermessungsschiffes Meteor in 

 der Ddnemark-Strasse u. Irminger See. Sitzgs.-Ber. Preuss. Akad. d. Wiss. XIX. 

 Berlin, 1931. 



