A note on the barotropic response of sea level to time‐dependent wind forcing

Abstract

This study examines the extent to which sea level variations at periods between 30 days and 1 year and spatial scales greater than 1000 km can be described by the wind‐driven linear barotropic vorticity dynamics. The TOPEX/POSEIDON altimetric observations of sea level and the wind products of the National Meteorological Center are used as the database for the study. Each term of the linear barotropic vorticity equation was evaluated by averaging over regions of 10°×10°. In most of the open ocean the result of the analysis suggests that the sea level variabilities at the scales considered cannot be fully described by the equation; the apparent net vorticity change is more than what can be explained by the local wind stress curl. In the few regions where the wind stress curl is strong enough to balance the vorticity budget, predominantly in the northeast Pacific and the southeast Pacific, the balance is basically achieved in terms of the time‐dependent topographic Sverdrup relation, namely, the balance between the advection of the planetary vorticity plus the topography‐induced vorticity and the forcing by the wind stress curl.

Global barotropic variability of the ocean in response to atmospheric forcing based on multichannel regression and Kalman filter techniques

“…The results are negative but consistent with the findings of other researchers, e.g. Fu and Davidson (1995). There can be many reasons why these models fail.…”

“…In addition we filtered the data to remove variability on the shortest scales of less than 40 days and the longest scales of longer than 200 days. It was shown in Fu and Davidson (1995) that this is the band where we would expect the linear vorticity balance with topography to be applicable. Our experiments with the gridded data produced results worse than the ones presented below.…”

“…Our present findings seem to support these ideas. Fu and Davidson, (1995) looked at the validity of the time-dependent linear vorticity balance in Pacific Ocean by using a single channel model. Their results were largely unsatisfactory, and the balance was rejected except for a few isolated points in mid-and high-latitudes.…”

Dynamics of global ocean heat transport variability

“…3.8, the only areas in the shallow water model with signifi cant sea-surface variability are in the northern Pacific and the Antarctic Circumpolar Current, in agreement with the results of Fu and Davidson 1995, Fu and Smith 1996, Chao and Fu 1995and Fukumori et al 1998. It supports the conclusion that in these particular areas, there is a significant sea-surface-height signature due …”

“…Furthermore, despite claims to the contrary Bryden et al 1991, there is observational evidence of deep ocean currents forced directly by time-varying wind stress fields Koblinsky and Niiler 1982;Niiler and Koblinsky 1985;Brink 1989;Koblinsky et al 1989;Luther et al 1990;Samelson 1990;Chave et al 1992;Niiler et al 1993. There is also observational evidence of large-scale wind forcing of seasurface height fluctuations Fu and Davidson 1995;Chao and Fu 1995;Fu and Smith 1996;Fukumori et al 1998.…”