Coupling an atmospheric model to an ocean model to study air-ice-ocean interactions in Antarctica: challenges and applications

Interactions between atmosphere, ice sheet and ocean play a crucial role in the Antarctic climate. For example, sea-air exchanges in leads and polynyas can strengthen cyclonic activities by warming and water vapour loading of air masses while associated sea heat loss and brine rejection modify water density and contribute to the dense water formation. Due to the harsh weather conditions in Antarctica, climate and ocean models appear as suitable tools to complement the scarcity of observations and to study the Antarctic climate. Nonetheless, only few models are able to represent typical processes found at high latitudes such as katabatic winds, drifting snow for the atmosphere or sea ice formation, accretion and deformation for oceans. Furthermore, due to their high non-linearity, those processes are difficult to model as they occur at different spatial and temporal scales. Current models are often forced by outputs: atmospheric conditions are provided to ocean models and ocean models outputs are used as surface conditions in atmospheric models meaning air feedbacks on ocean (or inversely) are muted. One can think models should be coupled at each time steps to take into account instantaneous interactions. Nonetheless, this method involves (too) high computational costs. The main challenge of this coupling is to take into account air-ice-ocean interactions and the temporal scale of associated processes in order to define an appropriate coupling time step. We will present both ocean and ice-atmosphere processes relative to polar climates and the specificities of the two models as well as technical coupling aspects.