<p>Large expanses of the Earth’s polar oceans freeze over each winter to form sea ice, which mediates key feedbacks on climate and polar biogeochemistry. The resulting sea ice forms a reactive porous matrix of ice crystals and interstitial brine: a so-called “mushy layer”. Convective fluid flows through porous sea ice drive chemical exchanges between ice, atmosphere, and ocean. This talk will first review how flow in mushy layers can be modelled, and then examine how high-porosity boundary layers cause localisation of flow near to mush-liquid interfaces. We will then explore whether the theory for mushy sea ice provides insight into the dynamics of water generation and transport within the outer ice shell of Enceladus, an icy moon of Saturn. Using a hierarchy of simplified models, we investigate convective boundary layers along frictionally heated faults in the ice shell, and show that the melt production could be sufficient to supply the water geysers of Enceladus.</p>
