Contributions of wind forcing, waves, and surface heating to sea surface height observations in the Pacific Ocean
Abstract
The dominant processes affecting sea surface height (SSH) variability observed by the TOPEX/Poseidon altimeter vary regionally in the Pacific; baroclinic Rossby waves, equatorially trapped Kelvin waves, steric response to seasonal heating, and the response to wind stress curl forcing are all important. The steric response to surface heating dominates seasonal SSH variability in the subpolar gyre and the eastern subtropical gyre. South of the Kuroshio Extension and south of 20°N in the eastern Pacific, the dominant contribution to SSH is from near-annual period Rossby waves. To quantify the wave energy, observed SSH was assimilated into a kinematic model of westward propagating waves. These waves account for >70% of SSH variance between 10°S and 10°N but only ∼30% between 10°N and 30°N. Although wave energy in the eastern Pacific is correlated with SSH anomalies at the equator, the much larger wave energy in the western Pacific is correlated with wind stress curl, suggesting that the Rossby 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 topographic Sverdrup balance is detectable over most of the North Pacific at latitudes as low as 10-15°N, as well as in the South Pacific, where it is seen north of 50°S. The decomposition of the SSH signal into propagating waves, an Ekman pumping response, and Sverdrup transport is consistent with the results from an isopycnal numerical model.
- Publication:
-
Journal of Geophysical Research
- Pub Date:
- September 1999
- DOI:
- 10.1029/1999JC900096
- Bibcode:
- 1999JGR...10420767V