Recent work on the turbulent transfer of scalar quantities following a step increase in the surface value of the scalar is directly applicable to the problem of estimating heat and mass transfer from Arctic leads in winter. If the turbulent flux is nondimensionalized as a Nusselt number N and the flow regime over the lead is parameterized by the fetch Reynolds number Rr, either the exponential transfer relation N = 0.08 × Rr0.76 or the linear relation N = 1.8 × 10−3Rr + 1100 describes the available data. Because N can be the Nusselt number for sensible heat, latent heat or condensate flux, Nusselt numbers of these scalar fluxes are equal for a given lead—Rr. The transfer relations and this Nusselt number equality are powerful estimation tools. With the transfer relations, turbulent fluxes can be computed from standard meteorological observables; and from the Nusselt number equality, partitioning of the turbulent fluxes can be evaluated— in particular, the partitioning of the heat flux between sen... Abstract Recent work on the turbulent transfer of scalar quantities following a step increase in the surface value of the scalar is directly applicable to the problem of estimating heat and mass transfer from Arctic leads in winter. If the turbulent flux is nondimensionalized as a Nusselt number N and the flow regime over the lead is parameterized by the fetch Reynolds number Rr, either the exponential transfer relation N = 0.08 × Rr0.76 or the linear relation N = 1.8 × 10−3Rr + 1100 describes the available data. Because N can be the Nusselt number for sensible heat, latent heat or condensate flux, Nusselt numbers of these scalar fluxes are equal for a given lead—Rr. The transfer relations and this Nusselt number equality are powerful estimation tools. With the transfer relations, turbulent fluxes can be computed from standard meteorological observables; and from the Nusselt number equality, partitioning of the turbulent fluxes can be evaluated— in particular, the partitioning of the heat flux between sen...