Turbulence and Mixing in Energetic Environment of the Coastal Waters of Sri Lanka

Abstract

In order to obtain first insights on the ocean turbulence and mixing in the waters around Sri Lanka, the microstructure measurements in the South Monsoon Current to the south of Weligama (along 80.5°E and near the shelf break) and in the East Indian Coastal Current in the Bay of Bengal to the east of Trincomalee (along 8°N) was conducted by National Aquatic Resources Research and Development Agency (NARA) of Sri Lanka aboard the research vessel Samuddrika. It is shown that in strongly startified pycnocline, which is dynamically detached from the low-saline surface mixed layer, the probability distributions of the logarithm of the kinetic energy dissipation rate 10 log ε follow generalized extreme value (GEV) model. This could be associated with the occurrence of rare highly-energetic turbulent patches in the pycnocline due to intermittent breaking of internal-wave and sporadic shear-induced instabilities. The mixing Reynolds number (a nomalized eddy diffusivity) was found to be a function of the gradient Richardson number, and followed the parameterization proposed by [1].