Contributions of wind forcing, waves, and surface heating to sea surface height observations in the Pacific Ocean

The dominant processes affecting sea surface height (SSH) variability obser ved by the TOPEX/Poseidon altimeter vary regionally in the Pacific; barocli nic Rossby waves, equatorially trapped Kelvin waves, steric response to sea sonal heating, and the response to wind stress curl forcing are all importa nt. The steric response to surface heating dominates seasonal SSH variabili ty in the subpolar gyre and the eastern subtropical gyre. South of the Kuro shio Extension and south of 20 degrees N in the eastern Pacific, the domina nt contribution to SSH is from near-annual period Rossby waves. To quantify the wave energy, observed SSH was assimilated into a kinematic model of we stward propagating waves. These waves account for >70% of SSH variance betw een 10 degrees S and 10 degrees N but only similar to 30% between 10 degree s N and 30 degrees N. Although wave energy in the eastern Pacific is correl ated with SSH anomalies at the equator, the much larger wave energy in the western Pacific is correlated with wind stress curl, suggesting that the Ro ssby waves there are locally forced. In addition to these planetary waves, the ocean response to wind forcing via Ekman pumping is observed in several places, specifically in the North Equatorial Current. A quasi-steady topog raphic Sverdrup balance is detectable over most of the North Pacific at lat itudes as low as 10-15 degrees N, as well as in the South Pacific, where it is seen north of 50 degrees S. The decomposition of the SSH signal into pr opagating waves, an Ekman pumping response, and Sverdrup transport is consi stent with the results from an isopycnal numerical model.