Observation and parameterization of oceanic convection – PLUME

Oceanic convection remains poorly understood even though it is one of the main driver of the oceanic dynamics. Convection can be penetrative (entrain water from below the mixed layer) or non-penetrative. While it is reasonably straightforward to formulate conceptual parameterizations of non penetrative convection in idealized settings, it remains challenging to extend the formalism to realistic settings of penetrative convection even for state of the art ocean models. In fact the most advanced parameterization schemes for oceanic convection are still calibrated based on atmospheric data. Moreover these parameterizations do not take into account the rotation of the earth which can substantially impact the individual and collective behavior of convective plumes. The first objective of this proposal is to build an observational database of convective events on the Coriolis Platform (the largest rotating tank of the world). We will complement this dataset with numerical simulations to explore many types of surface forcing and initial conditions. We will then combine these observations and model outputs with a robust theoretical framework to build a consistent parameterization of oceanic convection. Then, we will overcome the constraints of the mathematical framework of existing parameterizations and propose a data-driven approach to formulate a more generic parameterization. Last, we will test these parameterizations in coarse resolution ocean models. We will perform a sensitivity analysis of the oceanic heat uptake as a function of the free parameters to asses how and where our parameterizations can reduce uncertainty of climate projections.