The spring landscape of the Arctic tundra is dominated by a snow cover which is highly variable in depth owing to redistribution by wind. Because of dierent energy dynamics, this heterogeneous land cover produces a horizontal transfer of energy at a small scale, a process termed local advection. An advection eciency term (F S ), which represents the fraction of the sensible heat from snow-free patches which is advected to snow patches, was determined from ®eld studies and published model results. Energy balance calculations demonstrated the strong contrast between the two surface cover types that drive advective processes, and F S was found to decrease exponentially with decreasing snow cover fraction. The ®eld results suggest higher values of F S compared with the model results for single snow patches of varying size, but similar in magnitude to F S for multiple small snow patches. Utilizing exponential best-®t relationships between F S and fractional snow cover shows an increase in sensible heat ¯ux of over 100% for low snow cover fractions. When considering the average ¯ux over a composite snow and snow-free surface, the average sensible heat ¯ux obtained from weighting the ¯uxes for each surface by their respective areas underestimates the composite ¯ux when compared with when advection is considered.
This work provides a simple method to estimate the eect of local advection on sensible heat to snow patches and the average ¯ux from a composite surface during the snowmelt period, using only ¯uxes calculated independently for 0% snow cover and 100% snow cover and an estimate of F S . It demonstrates a good ®rst estimate of the role of advection, but for future study the in¯uence of wind speed, patch distribution patterns and fetch lengths needs to be considered more explicitly. This has important implications in studies of areal energy ¯uctuations over melting, patchy snow covers, basin water balance studies and regional and global climate modelling.