From observations in a High Arctic valley and ice-free fjord in Svalbard during March and April 2013 we show that, while some caution needs to be applied, ordinary slow-response instruments placed over a snow-water-snow surface can be effectively used as a proxy for more sophisticated measuring techniques at complex sites such as leads or a polynyas. The turbulent fluxes of momentum, sensible and latent heat were measured at three locations with a snow-water-snow fetch. At the snow site upwind of the water, the stability was generally stable, the momentum flux small, and the sensible heat flux positive. Over the water however, the internal boundary layer that was formed gave on average an increased vertical gradient in wind speed, temperature, and humidity and turbulent heat fluxes exceeding 400 W m−2. At the snow surface downwind of the water, the conditions were highly variable and all the fluxes were, on average, of very small magnitude. That the behaviour of the internal boundary layers can be highly variable is demonstrated through four case studies. This phenomenon is likely to increase in occurrence with a changing climate.