Evaluation of Scaling Approaches for the Oceanic Dissipation Rate of Turbulent Kinetic Energy in the Surface Ocean
Leonie Tabea Esters, National University of Ireland, Galway, AirSea Laboratory, Galway, Ireland, Brian Ward, National University of Ireland, Galway (NUIG), School of Physics, Galway, Ireland, Graig Sutherland, University of Oslo, Dept. of Mathematics, Oslo, Norway, Anneke Ten Doeschate, NUI Galway, Ireland, Sebastian Landwehr, National University of Ireland, Galway, Ireland, Thomas George Bell, Plymouth Marine Laboratory, Plymouth, PL1, United Kingdom and Kai H Christensen, Norwegian Meteorological Institute, Oslo, Norway
Abstract:
The air-sea exchange of heat, gas and momentum plays an important role for the Earth’s weather and global climate. The exchange processes between ocean and atmosphere are influenced by the prevailing surface ocean dynamics. This surface ocean is a highly turbulent region where there is enhanced production of turbulent kinetic energy (TKE). The dissipation rate of TKE (ε) in the surface ocean is an important process for governing the depth of both the mixing and mixed layers, which are important length-scales for many aspects of ocean research. However, there exist very limited observations of ε under open ocean conditions and consequently our understanding of how to model the dissipation profile is very limited. The approaches to model profiles of ε that exist, differ by orders of magnitude depending on their underlying theoretical assumption and included physical processes. Therefore, scaling ε is not straight forward and requires open ocean measurements of ε to validate the respective scaling laws. This validated scaling of ε, is for example required to produce accurate mixed layer depths in global climate models. Errors in the depth of the ocean surface boundary layer can lead to biases in sea surface temperature. Here, we present open ocean measurements of ε from the Air-Sea Interaction Profiler (ASIP) collected during several cruises in different ocean basins. ASIP is an autonomous upwardly rising microstructure profiler allowing undisturbed profiling up to the ocean surface. These direct measurements of ε under various types of atmospheric and oceanic conditions along with measurements of atmospheric fluxes and wave conditions allow us to make a unique assessment of several scaling approaches based on wind, wave and buoyancy forcing. This will allow us to best assess the most appropriate ε-based parameterisation for air-sea exchange.
