Microstructure measurements along a quasi-meridional transect in the northeastern Atlantic Ocean

Abstract

This study presents vertical profiles of turbulence parameters obtained in the upper 100 m of the northeastern Atlantic Ocean along a transect from tropical permanently stratified waters to subpolar seasonally stratified waters in July–August 2009. The focus is to fully characterize the vertical mixing along this transect for further studies related to phytoplankton and nutrient distributions. Derived values of temperature eddy diffusivity KT, of temperature variance dissipation rate χT, and of turbulent kinetic energy dissipation rate ε indicate a northward increase of turbulent mixing below the mixed layer. In the northern stations where the wind stress is sufficiently high, the vertical distributions of ε in the mixed layer follow the wind stress scaling. The related low wind-scaling factors, and the low values of ε encountered at this cruise, are in agreement with a strongly stratified upper water column at midday in summer.