The energy pathways of the submesoscales, which exist in the range between the mesoscale (on the order of 100 km) and the largest turbulent eddies(order of 1 m), will be quantified and parameterised so they can be incorporated into global climate models. This will be done using a numerical approach consisting of two different model studies specialised in both turbulent flows and regional ocean processes, aswell as a dedicated field program using the Baltic Sea as a "natural laboratory" for the measurement of submesoscale energy pathways.
The surface mixing layer (SML) is the ocean side of the air-seainterface through which the fluxes of energy, momentum and tracers have to pass in a coupled atmosphere-ocean system. Pathways and transformations of energy, momentum and tracers in the SML arecomplex, highly variable, and not sufficiently understood. Even in high-resolution ocean models, energy and momentum budgets are energetically inconsistent because the additional energy reservoirs and transformation processes due to unresolved processes (e.g.,mesoscale/submesoscale motions, surface waves) are either ignored or not correctly taken into account. In coarse-resolution climate models, the situation is even worse. The goal of this subproject is thereforeto investigate energy transport and transformation processes in the SML that are relevant for the ocean-atmosphere coupling in climate models.
Our major efforts to understand the energy budget of the SML will be conducted through the use of idealised Large Eddy Simulations (LES), high-resolution ocean modelling, and coordinated field surveys including high-resolution turbulence observations. The results from the LES and field work will be used in a realistic model to understand the energy pathways associated with submesoscale motions in the SML, and to test the developed parameterisations.
Burchard, H., Basdurak, N. B., Gräwe, U., Knoll, M., Mohrholz, V., and Müller, S. (2017). Salinity inversions in the thermocline under upwelling favorable winds. Geophysical Research Letters, 44, doi:10.1002/2016GL072101.