Spatially Unstable Waves in the Gulf Stream over the Carolina Continental Slope,
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)
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 01, 1982
- Accession Number
- ADP001054
Entities
People
- Mark E. Luther
Organizations
- Florida State University