interaction between boundary layer turbulence and submesoscale mixed layer eddies and its influence on upper ocean stratification

Metre-scale boundary layer turbulence and kilometer-scale submesoscale mixed layer eddies play crucial roles in upper ocean stratification. It is well established that the former generates significant vertical fluxes that mix the upper ocean, while the latter acts to restratify it. However, the interaction between these two multi-scale processes is not well understood, particularly when atmospheric forces are non-negligible. MPAS-Ocean was firstly used to investigate the influence of boundary layer turbulence on submesoscale eddy-induced restratification under various initial conditions. Two parametrizations K-Profile Parametrization (KPP) and k-ε were used to represent different forms of turbulence-induced destratification under the same forcing conditions. Comparison analysis was carried out by comparing the resulting submesoscale eddy-induced restratification. Among all cases, KPP exhibited a larger magnitude of vertical buoyancy flux than k-, indicating stronger turbulence-induced destratification. This enhanced destratification can lead to more intense submesoscale eddy-induced restratification, which largely compensates the turbulence-induced destratification. Furthermore, the value of the mixed layer eddy-induced streamfunction strongly depends on the strength of boundary layer turbulence, suggesting that parameterizations of these two processes may need to consider their interactions. To further explore the bidirectional interactions between these two processes, we are currently employing large-eddy simulation to resolve both. A spatial filter is used to separate the flow into submesoscales and small-scale turbulence. Preliminary results of the large eddy simulations, aiming to elucidate the interactions between these two processes, will be discussed.