Sea surface height observations of the 34°N 'waveguide' in the North Atlantic

Abstract

We present a study of the energetic zonal band at 34°N in the North Atlantic using a wavelet analysis of more than 8 years of TOPEX/POSEIDON altimeter data. It is already well-established in the literature that this zonal 'waveguide' is dominated by large-scale propagating features. The wavelet analysis yields sea surface height variance at a range of periods and wavelengths, allowing us to observe and quantify evolution of the features in space and time. Signal variance west of the mid-Atlantic ridge at 34°N is larger than to the east of the ridge: by a factor of -2 in the period band 0.5-0.9 years, in which baroclinic Rossby waves and eddies propagate. The period of the peak energy is reduced crossing the ridge from -1 year to -7-9 months, before rising again to the annual cycle on the other side. There is also evidence of energy peaks at periods of -2-4 years in the Gulf Stream region and east of the ridge.