This work focuses on heat fluxes and hydrodynamic of Ward Hunt Lake, Canada's most northern lake, as well as its response to climate variations. The project aims to implement a heat budget model, in order to improve our understanding of underlying mechanisms (water column stability, heat advection from waterflows during melting periods, influence of net solar radiation and air temperature variations, feedback effects). The first step is to build a unidimensionnal model, based on tne model from Vincent et al. (2008) implemented for the perennial-ice-covered Lake A, very close to Ward Hunt Lake. Then the model will be extended to two dimensions, along a vertical transect. Finally, the feasibility of extending it to a 3D model will be explored, in order to determine the entire data needed to do so. The project will be completed by a field campaign on Ward Hunt Island and northern Ellesmere Island, in the Canadian High Arctic, during 3 weeks in July 2017.