BATHYtriBliffcXJRAPn OBStlTVATIOT.'S 
r 
Bathythoraoi^apb (BT) caste wore taken at ^hour Interrale 
thr<(mf!!hont the oruiee, except wVoa/ in port or anohored off lalande« 
BT laotruraent auraber KK09297 was loot during the night of !ioromber 
5-6 1 auaber K3C09299 was need for the remainder of the ctnaiee* The 
calibrated grid supplied with the instrument wae need to determine 
temperature values at varioue dlepthe* From theae« e running plot 
was kept of the thermal etruoture of the eea along the emiee traek^ 
The BT easts regularly reached 200 metere depth| and frequently reached 
250 metere* 
The surface layer of the oos m normally is wellHoixsd and 
isothermalI or nearly ^09 This mixed layer usually has a sharply 
defined base below whioh is the thexneocllne %d^ere the temperature 
cools abruptly with depth* 
^Tien leaving Johnston Island (near 17°S) November 11, the base 
of the mixed layer was found at 75 aetera depth* As the ship proceeded 
sothweetward, the mixed layer became shallower* Its base rose 
gradually but steadily to a depth of only 30 meters between 10 ® and 9 ® 
north latitude* As the oold water below the mixed layer rose closer to 
the surfaeo, the temperature at I 50 aetera depth cooled steadily frem 
22*5®C^Mr Johnston to 13*5® at 10®N (see Figure 1), %i 8 region 
where the base of the surface mixed layer tilts upward toward the south, 
and the underlying water ooolo toward the south, is the region of the 
%re6tvardly flowing North Equatorial Current (ISFC)* 
« 
At about 10®N, the ship passed out of the ircC into the eastwardxy 
flowing Eqiiatorial Countercurrent (ECC)* The surface mixed layer 
