Mesoscale Variability Transition from the Western to the Eastern Atlantic along 48°N

Abstract

The North Atlantic low frequency variability along 48°N is described from 76 year-long velocity-temperature records obtained as part of the Topogulf project whose main objective was to document the effects of the Mid-Atlantic Ridge upon the circulation. The eddy energy is thermocline-intensified and shows a fivefold decrease eastward from 35° to 10°W. West of the ridge it penetrates more easily to the ocean floor. Between 1500 and 2500 m, sudden energetic bursts are observed and we argue that they are associated with the passage of sub-mesoscale concave cyclonic lenses depleted of Labrador Sea water. At nearly all locations a negative zonal momentum flux u′v′ is observed which may be linked to an energy transfer from the North Atlantic current. Eddy heat fluxes are also obtained and are directed up (down) the mean gradient west (east) of the ridge crest.