Ocean Science www.ocean-sci.net 1812-0784 1812-0792 4 1 2008 10.5194/os-4-99-2008 http://www.ocean-sci.net/4/99/2008/ http://www.ocean-sci.net/4/99/2008/os-4-99-2008.html http://www.ocean-sci.net/4/99/2008/os-4-99-2008.pdf 99 113 2008-03-18 Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model A. Lecointre T. Penduff P. Cipollini R. Tailleux B. Barnier Laboratoire des Ecoulements Géophysiques et Industriels, CNRS, UJF, INPG, Grenoble, France National Oceanography Centre, Southampton, UK Department of Meteorology, University of Reading, UK A 1/6° numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Rossby waves (RW), is first assessed by comparing the simulated amplitude and zonal phase speeds of Sea Level Anomalies (SLA) against TOPEX/Poseidon-ERS satellite altimeter data. Then, the (unobserved) subsurface signature of RW phase speeds is investigated from model outputs by means of the Radon Transform which was specifically adapted to focus on first-mode baroclinic RW. The analysis is performed on observed and simulated SLA and along 9 simulated isopycnal displacements spanning the 0–3250 m depth range. Simulated RW phase speeds agree well with their observed counterparts at the surface, although with a slight slow bias. Below the surface, the simulated phase speeds exhibit a systematic deceleration with increasing depth, by a factor that appears to vary geographically. 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