Gulf Stream Meander Propagation Past Cape Hatteras

Abstract

The propagation and growth characteristics of Gulf Stream meanders past the stream's separation point at Cape Hatteras are analyzed using yearlong time series from a mooring program sponsored by the Minerals Management Service, which included moorings imbedded in the Gulf Stream cyclonic flank both upstream (south) and downstream (north) of Cape Hatteras. In the upstream region, energetic meanders of 3?8-day period, 180?380-km wavelength propagate downstream along the Gulf Stream at speeds of 40?55 km day?1. This variability decays almost completely across the Gulf Stream separation, with growth in lower-frequency variability (30?120 day) in the downstream direction. Wavelength and phase speed in the 3?8-day band are strong functions of frequency, with increasing phase speed for increasing wavenumber. Phase speeds upstream from Cape Hatteras and across the Gulf Stream separation point are faster for a given wavenumber than downstream from Cape Hatteras, in keeping with prior published estimates. At the upstream end of the study site, both baroclinic and barotropic mechanisms contribute to the decay of 3?8-day meanders and growth of lower-frequency 30?120-day variability in the downstream direction. At the downstream end of the study region, the reverse holds, with both baroclinic and barotropic mechanisms contributing to growth of 3?8-day meanders and decay of lower-frequency 30?120-day variability.