Propagation and growth of Gulf Stream meanders between 75° and 45°W

Abstract

Analysis of the Gulf Stream path between 75° and 60°W indicates that the spectral signature of propagating and standing meanders is qualitatively similar to that observed for the upstream region 74°-70°W. Progressive, retrogressive, and standing meanders coexist at periods of several months and longer. The amplitude-dependent dispersion relation obtained for the region 75°-45°W demonstrates the decrease of phase speed as the amplitude increases; the dependence of phase speed on amplitude is found to be stronger than that on wavelength. The average phase speed decreases with downstream distance primarily due to the downstream increase of meander amplitude. Consequently, a relation between phase speed and wavelength for the region west of 70°W, averaged over all amplitudes, is not uniformly valid for a larger domain. Furthermore, downstream propagating meander troughs are steeper and travel more slowly than meander crests. The average stationary wavelength, 700-800 km for 75°-60°W, is much shorter than that predicted based on an equivalent barotropic, β-plane thin-jet model. The most energetic meanders have a period of 46 days and a wavelength of 427 km. The period of the fastest-growing meanders is approximately 40 days, close to the period of the most energetic meanders. The wavelength of the fastest-growing meanders, about 350 km, is shorter than the wavelength of the most energetic meanders. The New England Seamounts do not have a significant effect on the most energetic meanders. However, meanders having periods either shorter or longer than the period of the most energetic meanders are affected by the seamounts. For long-period meanders, their lateral excursions seem to be constrained by the seamounts.