Turbulence variability in the upper layers of the Southern Adriatic Sea under a variety of atmospheric forcing conditions

Abstract

As part of the DART06B observational campaign in late August 2006, a microstructure profiler was deployed to make turbulence measurements in the upper layers of the Southern Adriatic Sea. Of the nearly 300 total casts, 163 were made near Station B90, where various moorings were deployed in the 90 m deep water column to measure water column properties and meteorological and surface wave conditions. We were able to measure turbulence properties in the upper layers under a variety of atmospheric forcing conditions that included strong wind forcing, night-time convection, mixed convection and wind forcing, weak wind forcing and strong insolation. The resulting dataset provides a kaleidoscope of turbulence properties and turbulent mixing above, below and in the strong pycnocline present at a depth of 15 to 25 m in the coastal waters of the Southern Adriatic Sea during late summer. A slightly modified scaling of the dissipation rate of turbulence kinetic energy in the mixed layer (ML), based on the observed friction velocity u* and the surface buoyancy flux Jb0, reproduces the measured values reasonably well. In the interior, below the ML, the dissipation rate scales like , where LT is the Thorpe scale and N is the buoyancy frequency. Analysis of velocity and density profile measurements from Station B90 and the nearby station B75 suggest that anticyclonic eddies and near-inertial waves can interact in these coastal waters to produce significant horizontal advective density fluxes in the pycnocline.