Evidence for bottom-trapped topographic Rossby waves from single moorings

Abstract

Current-meter observations near 39°N, 70°W, on the continental rise, provide evidence that the motions with periods of 1 to 2 weeks are dominated by baroclinic topographic Rossby waves which decay upward from the bottom. Temperature and up-slope velocity are coherent and in quadrature at these frequencies, as predicted. The kinetic energy structure versus depth is consistent with horizontal wavelengths of 100 to 200 km. The spectra drop abruptly for periods shorter than a week, the shortest period the model says the slope and stratification around Site D can maintain. The principal axis of the velocity shifts from nearly perpendicular to the isobaths at 1-week period to nearly along the isobaths at long periods, in satisfactory quantitative agreement with the model.