Accession Number : ADP001054

Title :   Spatially Unstable Waves in the Gulf Stream over the Carolina Continental Slope,

Corporate Author : FLORIDA STATE UNIV TALLAHASSEE MESOSCALE AIR-SEA INTERACTION GROUP

Personal Author(s) : Luther,Mark E.

Report Date : APR 1982

Pagination or Media Count : 25

Abstract : A numerical model is presented investigating the unstable normal modes of oscillation of a realistic boundary current. The model background current approximates the Gulf Stream south of Cape Hatteras, N.C., possessing both vertical and horizontal shear, and flowing along a sloping bottom topography. Small amplitude, alongshore propagating perturbations to the background flow are sought with real frequency and complex alongshore wave number as eigenvalues. A non-zero imaginary component of the wave number implies that the wave amplitude grows in the alongshore direction. Observations in the Gulf Stream south of Cape Hatteras, N.C., have revealed a persistent wave-like meander pattern with a dominant period of 8 days, henceforth called the 8-day wave. This wave form propagates in the downstream direction with a phase speed of about 40 km/day and is uncorrelated with any known forcing. The observed 8-day wave appears as a eigenmode of the model. The perturbation velocity fields from the model 8-day wave are consistent with observations. The instability mechanism of the model wave is of the mixed barotropic-baroclinic type, with the majority of the perturbation energy coming from the potential energy of the background flow (about 80%). Warm filaments are formed on the inshore side of the background current, separated from the core of the current by a cool dome of upwelled water. (Author)

Descriptors :   *Ocean currents, Background, Gulf Stream, Variations, Waves, Stability, North Carolina, Continental slopes

Distribution Statement : APPROVED FOR PUBLIC RELEASE