Influence of snow processes on sea ice : a model study

Sea ice, the result of seawater freezing at high latitudes, plays a key role in the global climate system. It is both a diagnostic and prognostic factor with regard to climate change. Besides, it is a platform for snow to accumulate on and, because this platform moves and deforms with ocean currents and winds, its snow cover is astoundingly heterogeneous. Snow processes on sea ice have crucial consequences in driving the evolution of sea ice, at a cascade of temporal and spatial scales. Although sea ice models have been developed for decades, the representation of snow in these models has remained under-addressed. This doctoral thesis is a contribution toward the improvement of the snow component in large-scale sea ice models. For the first time, a representation of snow physics of intermediate complexity was introduced in a model of this kind, providing the tools to assess the influence of snow on sea ice. Using those tools, we have shown in particular the importance of accounting for wind-driven snow processes and properties in models in order to realistically simulate the evolution of perennial sea ice. As such, this thesis opens the way for snow-related improvements in climate models and provides modelers with some guidance in achieving this task. As the better quantification of the impacts of snow processes on sea ice goes through the adequate constraining of their parameterization, extensive In Situ observations are required. This thesis also gives some directions for these future investigations.