The use of combined information from expendable bathythermograph and sea level observations for ocean monitoring requires the establishment of relations between sea level, thermocline depth, heat content, and dynamic height. Sea level fluctuations are a good measure of thermocline depth fluctuations in the tropical Pacific between about 15 ¿N and 15 ¿S and allow the determination of changes of upper-layer volume. Sea level is also a good measure of heat content, and useful correlations extend to higher latitudes. Dynamic height and sea level fluctuations agree only in those areas where the thermal structure resembles a two-layer system very well, and good correlations are restricted to a narrower area. The combination of bathythermograph and sea level observations will allow a better mapping of the changes of thermocline topography, heat content, and dynamic height for the monitoring of climatic changes in the tropical Pacific.