Improving Thorpe-length scale based estimates of turbulent kinetic energy dissipation rates in stably stratified turbulent flows

A linear relationship between the Thorpe (vertical overturn) length scale LT and Ozmidov length scale LO is common assumption that is often invoked to estimate the dissipation rate of turbulent kinetic energy ε. This assumption is particularly attractive since vertical scales of overturns can be calculated using sorting algorithms from inversions in standard measurements of density profiles obtained from Conductivity-Temperature-Depth (CTD) measurements in the ocean. However, a number of studies highlight the lack of a linear relationship between LT and LO and indicate that inferred estimates of ε may be biased high by up to an order of magnitude. In this study, an attempt is made to provide a physically based correction to the Thorpe-inferred dissipation rates that is consistent with 'true' estimates of ε as obtained from direct numerical simulations (DNS) of stratified turbulence. The implications of these findings for improved estimates of ocean mixing rates will be discussed.