CHEMICAL RESULTS OF LAST CRUISE OF CARNEGIE 



3. Zones 1 and 2 correspond approximately to what 

 Defant (1928) calls the troposphere , the stratum in which 

 there is an active circulation with relatively large vari- 

 ations in temperature and salinity. Its lower limit cor- 

 responds, according to Sverdrup (L-A, p. 83), to the 10° 

 isotherm. In the Pacific this is found at 500 to 650 me- 

 ters below the surface. 



4. The layer between the troposphere and the sea 

 bottom, Defant designates as the stratosphere. Here 

 the temperature and salinity changes are relatively 

 small and the water movements are slow. 



Since the water layers enumerated above are based 

 on the distribution of the physical conditions, and since 



the latter do not always correspond to the distribution of 

 chemical substances, the names of the layers are not 

 always used in their strict physical sense but often to 

 designate only the distribution of the chemical sub- 

 stances. The distribution of these, as will be shown 

 later, is the result not only of physical forces but of bi- 

 ological agencies as well. 



A brief description of the geographic sections, to- 

 gether with some of the outstanding hydrographic condi- 

 tions encountered, including the thickness of the convec- 

 tion layer as determined by the depth to which uniform 

 physical conditions were found, follows. 



CARNEGIE SECTIONS: GEOGRAPHIC POSITIONS AND HYDROGRAPHIC CONDITIONS 



Atlantic Ocean 



Section 1 (Stations 24 to 13) .--Thisisa more or less 

 north and south section through the North Atlantic from 

 the Grand Banks of Newfoundland to latitude 8° north. 

 Station 13 is located on the Grand Banks, stations 14 to 

 16 are in the Western Atlantic Basin, stations 17 and 18 

 on the Atlantic Ridge, and stations 19 to 24 in the east- 

 ern basin. The center of this section is in the Sargasso 

 Sea which is characterized by warm water of high salin- 

 ity. This is centered at stations 18 and 19. To the north, 

 at station 15, there is a convergence of the cold water of 

 the Grand Banks and the warm Atlantic water. This is 

 shown by the temperature and salinity charts to a depth 

 of 1500 meters. The stations south of the Sargasso Sea 

 are in the North Equatorial Drift. The Intermediate 

 Antarctic Current from the south comes in at 700 me- 

 ters and extends as far north as station 20. The convec- 

 tion layer is about 50 meters thick in the central part of 

 the section and about 25 meters thick elsewhere. 



Section II (Stations 34 to 25). --This section runs 

 approximately east and west in the tropical North Atlan- 

 tic along the parallel of about 12° north from Panama to 

 37° west longitude. Stations 34 to 31 are in the Carib- 

 bean Sea, stations 30 to 28 are in the western basin of 

 the Atlantic, station 27 is on the Atlantic Ridge, and sta- 

 tions 25 and 26 are in the eastern basin. The stations in 

 the eastern part of this section are in the North Equato- 

 rial Drift. Those in the western part are in the continu- 

 ation of this drift into the Caribbean. In the salinity 

 chart the Intermediate Antarctic Current is clearly seen 

 coming in at the south at 700 meters and extending into 

 the Caribbean beyond station 31. The convection zone 

 throughout this section is about 25 meters thick. 



Miscellaneous Atlantic Stations . --Stations 1 to 12 

 have not been utilized in the construction of vertical 

 sections. Stations 1 to 6 were occupied at the beginning 

 of the cruise when the apparatus and technique were be- 

 ing perfected so that the results at these stations may 

 not be so accurate as at the later stations. The stations 

 are located between the United States, the British Isles, 

 Iceland, and Newfoundland. 



Pacific Ocean 



Section III (Stations 60 to 72 and 40 to 37) .--This 

 section lies in the southeastern Pacific. It begins at ap- 

 proximately latitude 40° south and longitude 100° west 

 and runs north-northeast to the coast of Peru at latitude 

 17° south whence it continues northward to the Gulf of 



Panama. Stations 60 to 65, south of 30° south, are in a 

 branch of the South Pacific East Drift which is an appre- 

 ciable current to a depth of 300 meters. Stations 66 to 

 72, between latitudes 30° and 10° south, are in the 

 northward-flowing Peruvian or Humboldt Current. Sta- 

 tions 39 to 37 are included in an anticyclonic movement 

 in the Gulf of Panama. Stations 67 to 72 are in a region 

 off the coast of Peru where upwelling occurs in the up- 

 per 300 meters. The intermediate water off the South 

 American coast flows westward between 600 and 700 

 meters. In this section the thickness of the convection 

 layer is variable, ranging from a few to 40 meters. 



Stations 35 and 36 .--Stations 35 and 36 in the Cen- 

 tral' American Bight were not included in any section. 

 They are situated in the same latitude as that part of 

 Section III which lies between stations 37 and 39 but are 

 closer inland than the latter stations. 



Section IV. (Stations 51 to 45) . --This section is also 

 in the southeastern Pacific, approximately north and 

 south from latitude 29° south to latitude 5° south and be- 

 tween longitudes 115° and 105° west. In the northern 

 part of the section the currents are westerly, in the 

 southern part they are very indefinite with a possible 

 easterly movement. The convection layer is somewhat 

 thicker than in the last section. At station 48 it is 80 

 meters, at station 45 it exceeds 60 meters, but at station 

 51 it is less than 25 meters. 



Section V (Stations 162 to 148 and 134 to 130) . --This 

 section runs northeastward from the Samoan Islands 

 (latitude 14° south, longitude 168° west) to San Francis- 

 co (latitude 37° north). It cuts through several current 

 systems. To the extreme northeast is the California 

 Current, with upwelling within the upper 400 meters, off 

 the coast of California. Stations 150 to 151 are in the 

 westward-flowing North Equatorial Drift. Station 153 is 

 in the most active part of the Equatorial Countercurrent, 

 which is a swift current but extends only to a depth of 

 200 meters. Stations 154 to 156 are south of the most 

 active part of this current but the water movement at 

 these stations also is mostly easterly. South of the equa- 

 tor the currents are westerly, stations 157 to 159 being 

 in the strongest part of the South Equatorial Drift. In 

 the equatorial currents there are irregular vertical 

 water movements. Within the countercurrent there is a 

 strong descending motion and at its borders, i.e., at the 

 inner borders of the North and South Equatorial drifts, 

 there are strong ascending movements, the more pro- 

 nounced of these being in the North Equatorial Drift. 

 The convection layer is about 50 meters thick from sta- 

 tions 130 to 149 but decreases to less than 10 meters at 



