Basinwide very low-frequency (VLF) modes with zonal uniformly deepening and
shoaling of the equatorial thermocline are found as solutions of linear sh
allow-water equations with the meridional basin boundaries under an equator
ial beta plane. They can be understood as the free heat-content recharge os
cillations. The interannual VLF modes had been recognized as the essential
part of the coupled recharge oscillator theory for the El Nino-Southern Osc
illation. It is suggested that the decadal VLF modes may also be transforme
d into coupled modes relevant to the Pacific decadal climate variability th
rough the ocean-atmosphere interaction in the Tropics.