Observations of Topographic Rossby Waves on the Continental Margin off Nova Scotia

Abstract

Bursts of topographic-Rossby-wave energy have been observed in data recorded by an array of current meters moored on the outer continental shelf and slope off Nova Scotia north of the Gulf Stream. The waves persist for three or four cycles during which both the period (10 to 23 days) and the amplitude of the oscillations are modulated. At least four different events have been observed over approximately one year and appear to be associated with warm eddies shed by the Gulf Stream. One particularly clear event, dealt with in detail, had a period of 21 days, an offshore scale of 175 km and an offshore phase speed of 8 km day?1. The array of moorings was too small to resolve accurately the longshore scale or propagation direction. The wave appears to be barotropic (nearly uniform in amplitude and phase) at the 1000 m isobath, but increasingly baroclinic in both cross-slope directions. Deep-water kinetic energy associated with the wave appears to be uniformly distributed over the upper portion of the rise.