In the (Sub)tropical oceans (Zone 1), except for the
equatorial upwelling Pacific, waters with a temperature of
20C and salinity of 35 have AT values of about 2305 mmol
kg1 for the entire (Sub)tropics. Thus, at SST = 20C and
SSS = 35, AT values in these warm waters are forced to an
intercept of 2305 mmol kg1 for the (Sub)tropics (see the first
equation in Table 1).