Generation and Propagation of Annual Rossby Waves in the North Atlantic

Abstract

Results of a nonlinear quasi-geostrophic mode model on the β-plane with topography and coastal geometry of the North Atlantic in the area 10°–50°N, 10°–80°W are presented. Two modes are used in this study. The baroclinic one is based on the mean density profile from the Levitus dated at 30°N. Mean and annual variations of the wind stress curl, which drive the model, were obtained from the Bunker climatic atlas. Annual Rossby waves emanating off the eastern coast are strongly influenced by the Mid-Atlantic Ridge. West of the MAR a relative minimum of energy is observed. The waves are influenced and modified by variable bottom topography. In the western basin two regions are identified where Rossby waves are generated: the Gulf Stream and its extension towards the east and the southern flank of the subtropical gyre. Compared to the North Pacific, annual Rossby waves seem to be less energetic in the North Atlantic.