izo 



06a-H03O - 

 S2I 



323 



324 



325 



LATITUDE (NORTH) 

 LONGITUDE (WEST) 

 SURFACE SALINITY ' 

 SURFACE TEMPERAT 



Jl STANCE (NAUTICAL MIL£Sf 

 I g343 



30* 56' 39*36' 

 68-52' 66*49 



3sa9 15 ao 



'T05 I80S I9S0 ;030 2120 2200 



sa*28' 38*23" 38T8.5' 3B-(4' 58*10' JB*06' 



6a**5' 68*42' 6e"38' 68*35' 68*31' 68*28' 



35 86 36-63 



Figure 19.-Transect Ill-Section 16, June 2, 1963. 

 (iSee caption for fig. 13.) 



14); and on the th'rd crossing, between BT's 

 197 and 199 (fig. 13). 



The right boundary was crossed only once 

 along transect ^I. Unfortunately, no surface 

 temperatures are available because the recorder 

 was temporarily out of order. Since the tem- 

 perature difi'erence between the Sargasso Sea 

 and the Gulf Stream was 4° C, the boundary 

 may have been even more distinct than along 

 transect I. 



The right boundary was crossed only once 

 along transect III also; the crossing is shown on 

 the surface temperature record between BTs 

 358 and 359 (fig. 21). The isolated peak on the 

 trace represents an occasion when the ship was 

 steered back and forth quickly across the 

 boundary along legs about 200 m. long. At this 

 time, the boundary was distinctly indicated by 

 surface conditions. The sea was choppy on the 



Gulf Stream side but relatively smooth on the 

 Sargasso Sea side, with no zone of transition- 

 just a sharp line. 



The right boundary was crossed again at lat. 

 37°12' N. and long. 69*^23' W., while the vessel 

 traveled from transect III to transect II (fig. 

 1; also see surface temperature trace in fig. 2). 

 The boundary was crossed within 5 miles (9.3 

 km.). Since we were running obliquely to the 

 Stream, the actual gradient at the boundary 

 must have been considerably steeper than indi- 

 cated on the trace. 



The presence of a distinct right boundary on 

 all occasions contradicts statements in the liter- 

 ature on the subject, to the effect that no de- 

 tectable boundary exists between the Gulf 

 Stream and the Sargasso Sea (Iselin, 1936, 

 1940). Possibly, of course, the boundary is not 

 marked in the warm season, when the tempera- 

 ture of the surface waters is higher in the 

 Sargasso Sea than in the Gulf Stream. Per- 

 haps the right boundary is more typical of con- 

 ditions in winter and spring than in other 

 seasons. 



WIDTH OF THE GULF STREAM 



The Gulf Stream was about 50 miles (92.6 

 km.) wide along transects I and II, but about 

 70 miles (129.6 km.) along transect III. The 

 greater width along transect III may not have 

 represented a greater actual width of the Gulf 

 Stream, but only a transient deformation of its 

 right side. A similar deformation is indicated 

 for the same day at this location in the U.S. 

 Naval Oceanographic Oflice sea-surface tem- 

 perature chart. 



ENVIRONMENT OF THE GULF STREAM 



The Gulf Stream structure, at the surface 

 bounded on the left and right as defined in the 

 previous section, consisted of a warm core 

 flanked by rather small horizontal temperature 

 gradients of varying widths. The warm core 

 extended to depths of 60 to 80 m. over a width of 

 25 to 35 miles (46.3-64.8 km.). Mean values 

 are given to facilitate comparison of the sur- 

 face properties of the slope water, the Gulf 

 Stream as a whole, the warm core of the Gulf 

 Stream, and the Sargasso Sea (table 1). The 

 slope water values are from five stations along 



GULF STREAM OFF CHESAPEAKE BAY 



405 



