Three years of TOPEX/POSEIDON altimeter data are analyzed with respect to large-scale fluctuations in sea surface height observations and underlying physical processes. In midlatitudes the most conspicuous feature in the large-scale changes in sea surface height are related to surface buoyancy fluxes, predominantly surface heat fluxes. The next prominent variability on subannual timescales is the adjustment of the ocean to varying winds stress fields in terms of planetary waves. The degree to which basin-scale sea surface height variations relative to the steric component can be described as a time-dependent Sverdrup balance is addressed for the Pacific Ocean. If a flat bottom ocean is assumed, a significant correlation of meridional mass transport variations inferred from TOPEX/POSEIDON and a simple Sverdrup model can be found in the Pacific Ocean north of 40 ¿N, but it fails elsewhere. Numerical ocean general circulation models show a good agreement with the TOPEX/POSEIDON observations in all those components of ocean variability and allow further insight into the dynamics that govern observed sea surface height changes.¿ 1997 American Geophysical Union