We have transmitted low-frequency acoustic signals from a source on Pioneer Seamount off California to receivers in the north and central Pacific. Receivers consist of 11 horizontal SOSUS arrays maintained by the US Navy and 2 vertical ATOC arrays off Hawaii and Christmas Island.
Comparison of the acoustic measurements of heat content with satellite altimeter measurements of surface elevation, restrained by a GCM model,show that about half the seasonal and year-to-year changes in sea level are attributable to thermal expansion. The annual cycle of heat flux is 150 +- 25 W/m2(<italic>exponent)</italic>. Meteorological estimates of surface heat flux require a surprisingly large seasonal cycle in the advective heat flux.