10 



CHEMICAL RESULTS OF LAST CRUISE OF CARNEGIE 

 REGIONAL DISTRIBUTION 



Carnegie Sections 



Section I, stations 24 to 13: more or less north and 

 south from Grand Banks of Newfoundland to latitude 8° 

 north between longitudes 35° and 50° west. --At all sta- 

 tions except the two most northerly stations, 13 and 14, 

 the phosphate content in the surface layer is relatively 

 low. In the central part of the section, where there is a 

 sinking of warm water of high salinity, the line of 10 mg 

 PO4 per cubic meter is found at a depth of more than 

 200 meters. In this area the transition zone also is much 

 expanded, the increase in phosphate values with in- 

 crease in depth being very gradual. The maximum of 

 phosphate occurs at 1000 meters and is represented by 

 less than 125 mg PO4 per cubic meter. To the north and 

 to the south of this area, much higher values occur in 

 the upper layers. To the north, where the water is 

 colder, values above 150 mg PO4 per cubic meter were 

 observed. At station 15, where there is a convergence 

 of cold and warm water (see p. 4), the lines of equal 

 phosphate content are bent downward. In the southern 

 part of the section, high values were observed in the 

 Antarctic Intermediate Current, reaching 275 mgat 7000 

 meters at station 22. In the stratosphere the phosphate 

 content is somewhat more than 125 mg PO4 per cubic 

 meter in the northern part of the section, but decreases 

 to about 100 mg in the central part, and again increases 

 slightly to the south. 



Section II, stations 34 to 25: approximately east and 

 west in the tropical North Atlantic along the parallel of 

 about 12° north from Panama to longitude 37° west.-- 

 There is a scarcity of phosphate at the surface through- 

 out the section, water containing less than 10 mg PO4 

 per cubic meter extending to 50 and 100 meters at all 

 the stations as shown by the 10-mg line. The transition 

 zone is usually in the upper 500 meters in the western 

 and central parts of the section but rises toward the east 

 and at station 25 it is in the upper 200 meters. The max- 

 imum phosphate values occur between 500 and 1000 me- 

 ters and vary from about 125 mg to more than 275 mg 

 PO4 per cubic meter. In the eastern part of the section 

 high values are found in the Antarctic Intermediate Cur- 

 rent at 700 meters. Two other areas of high phosphate, 

 also due to antarctic water (1-A, pp. 88, 89, 96), occur 

 in the central part of the section. In the stratosphere 

 the phosphate values decrease below the maximum to 

 about 100 mg PO4 per cubic meter. 



Section III, stations 60 to 72. 40 to 37: in the south- 

 eastern Pacific, beginning at approximately latitude 40° 

 south, longitude 100° west, extending north-northeast to 

 the coast of Peru at latitude 17° 30' south, thence north- 

 ward to the Central American Bight. --Phosphate at the 

 surface is nowhere reduced in this section. The surface 

 values between stations 37 and 40 are from 15 to 25 mg 

 PO4 per cubic meter. From stations 40 to 71 they range 

 between 25 and 50 mg PO4 per cubic meter. At station 

 70 the concentration of phosphate reaches 103 mg PO4 

 per cubic meter. South of this it decreases but never 

 reaches 20 mg PO4 per cubic meter. 



In the upper 300 meters the phosphate section shows 

 a marked similarity to the temperature section, the line 

 representing 75 mg PO4 per cubic meter following the 

 general course of the 15° isotherm. The effect of up- 

 welling, which is shown by the temperature and salinity 



sections at stations 68 to 70, is quite evident also in the 

 phosphate section where all the lines are raised toward 

 the surface. 



The Antarctic Current of low salinity entering from 

 the south at about 400 meters is not apparent in the phos- 

 phate section but its effect is easily recognized in the 

 curves showing the vertical distribution of phosphate 

 (I-B, pp. 62-67). From stations 60 to 66 there is a zone 

 of comparatively low phosphate centered at about 400 

 meters. 



The phosphate maximum occurs at about 1800 me- 

 ters in the south but gradually rises to about 600 meters 

 in the north. The phosphate content is variable, ranging 

 from 225 to 325 mg PO4 per cubic meter. The Carnegie 

 observations indicate that the bottom water in this re- 

 gion contains between 200 and 250 mg PO4 per cubic 

 meter. 



Stations 35 and 36: in the Central American Bight, 

 east of the north end of Section III. --The phosphate con- 

 tent of the water at these stations is very similar to that 

 at the stations to the west, or to that of the northern part 

 of Section III. 



Section IV. stations 51 to 45: in the southeastern 

 Pacific extending approximately north and south from 

 latitudes 29° to 5° south, between longitudes 115° and 

 105° west.' --In the surface layer the concentration of 

 phosphate is everywhere 10 mg PO4 per cubic meter or 

 more. From south of station 46, however, and centering 

 at station 48, the 25 -mg PO4 line extends to almost 300 

 meters, indicating relatively low values in the upper levels 



The phosphate transition zone in general follows 

 the thermocline, being found at increasingly low levels 

 toward the south. The tongue of antarctic water from 

 the south, which is shown in the salinity section, is not 

 evident in the phosphate section but is indicated in the 

 station curves of the vertical distribution. The level at 

 which the phosphate maximum occurs, varies between 

 750 and 1400 meters. The magnitude of the maximum 

 values increases from less than 175 mg at station 50 to 

 more than 225 mg PO4 per cubic meter north of station 47. 



Section X. stations 51 to 52. 55 to 60: in the south- 

 eastern Pacific extending southeastward from latitude 

 29° south, longitude 115° west to latitude 40° south, 

 longitude 98° west. --At the surface the phosphate values 

 show a continuous increase from northwest to southeast. 

 Between stations 51 and 57 there is less than 10 mgP04 

 per cubic meter, whereas in the southeastern part of the 

 section the phosphate content is greater, being 50 mg 

 per cubic meter at station 60. 



The layer of maximum phosphate is somewhat indef- 

 inite, the concentration continuing to increase below 2000 

 meters at stations 55, 58, and 59. 



Stations 53 and 54: north of Section X, north of sta- 

 tion 56, east of station 51, south of Easter Island. --At 

 these two stations the vertical distribution of phosphate 

 is very similar to that at stations 51 and 52 to the west. 

 The surface values vary from 9 to 13 mg PO4 per cubic 

 meter. The transition zone extends to 500 meters as 

 at station 51 to the west, rather than to 350 meters as at 

 station 56 to the south, indicating that the change in con- 

 ditions in Section X, which extends from northwest to 

 southeast, from stations 51 to 60, represents a change 

 in a north and south direction r?ther than in an east and 

 west direction. 



