Geostrophic Control with Wind Forcing: Application to Bass Strait

Abstract

A conceptual model of the low-frequency flow in a strait of finite length, based on the derivation geostrophic control, is compared with a more complete model that includes the reflection of Kelvin waves at the ends of the strait. The low-frequency sea level responses of the two models are identical for Bass Strait The reason for the agreement, in straits of width less than one external Rossby radius, is that the Kelvin wave structure is approximately linear over the length and width of the strait. The low-frequency sea level response can be characterized as follows: the pressure-forced mode tilts down in the direction of flow, and the wind-forced mode tilts up in the direction of flow. Both modes are in geostrophic balance in the cross-strait direction.