Gulf Stream–Generated Topographic Rossby Waves

Abstract

An inverse ray tracing model is applied to observations of 40-day topographic Rossby waves on the continental slope off of Cape Hatteras, North Carolina, to determine their origin. The rays are traced seaward and extend into the deep Gulf Stream, where the bottom slope remains strong enough that topographic β dominates planetary β. This enable coupling to occur between eastward propagating Gulf Stream meanders and topographic waves with eastward phase speed and matching zonal wavelength. Previous satellite observations indicate that the most frequently occurring Gulf Stream meanders have a period of 40 days and the model reveals that, as these meanders pass a topographic bend near 71°–72°W, they are able to couple to the observed topographic waves traced back from Cape Hatteras. The 40-day Gulf Stream meanders occur in bursts, which leads to associated bursts of the topographic waves.