Wind-Forced Sea Level Variability Along the West Florida Shelf (Winter, 1978)

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Abstract

Coastal tide gage and meteorological records from Pensacola to Key West for the period January–April 1978 have been examined for low-frequency fluctuations. The dominant 6-day period signals in sea level, alongshore wind stress, and atmospheric pressure were coherent over the entire shelf and propagated southward, consistent with the movement of cold fronts through the area. Sea level response tagged the local wind stress by 18 h (in the north) to 9 h (in the south). In response to a 1 dyn cm⁻² alongshore stress, sea-level amplitudes were largest (∼60 cm) where the shelf is widest (200 km) and undergoes an abrupt bend, and were ∼30 cm elsewhere; large transient alongshore sea level slopes, on the order of 10⁻⁶, were thus set up. A linear steady-state shelf circulation model (Hsueh, 1980) is used to explore the sea level distribution that is in frictional equilibrium with a wind stress of given orientation. For a bottom resistance coefficient of 0.014 cm s⁻¹, a value suggested by an analysis of February current measurements on the inner shelf, the model results resemble the observed response. Modeled responses are trapped to within the inner shelf (depths < 30 m) with an e-folding scale of ∼60 km. Experimentation with open-ocean forcing, idealized as a shelfbreak sea level distribution induced by various hypothetical configurations of the Loop Current, shows that changes in the equilibrium coastal response are negligibly small.

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