Observations of the vertical structure of the oceanic boundary layer

Abstract

The vertical structure of the surface layer of the ocean is examined at inertial and lower frequencies using observations made from the research platform FLIP in the late winter of 1990. The analysis isolates the shear supported by density gradients at the base of the mixed layer from that found within the layer. Near‐inertial frequency shear variability is most energetic at the base of the shallow, well‐mixed isothermal surface layer. At lower frequencies, significant shear is found within the surface layer. The wind‐driven transport is in good agreement with the Ekman transport and is divided almost equally between the surface layer and a less well mixed layer just below. The vertical structure of the wind‐driven flow within the surface mixed layer varies with frequency; it is slab‐like near the inertial frequency but strongly sheared at the lowest frequencies.