Abstract : Observations from the Cassini spacecraft imply the presence of a global ocean underneath Enceladus' ice shell, with ongoing hydrothermal activity at seafloor. Previous numerical simulations showed that convection in Enceladus' unconsolidated core generates enough dissipation to sustain the ocean while producing a strongly heterogeneous seafloor heat flux that may explain the ice topography (Choblet et al., 2017). Yet, how the ocean in-between connects the deep core to the surface ice shell is the missing piece of the Enceladus puzzle. We fill this gap by performing 3-D numerical simulations of the ocean with very heterogeneous boundary conditions derived from core simulations (Choblet et al., 2017). We show that a strong zonal flow inhibits heat transfer at low latitudes. The resulting heat flux pattern at the ocean/ice interface shows quantitative agreement with an observations-based ice shell model (Cadek et al., 2019). Using passively advected tracers, we predict rising times for hydrothermal products of hours to weeks, compatible with previous predictions. Our results provide a complete self-consistent model of the heat transfer in Enceladus explaining the global characteristics of this moon: global ocean, strong dissipation, thinner ice-shell at the poles and seafloor activity.