Sensible heat flux and local advection over a heterogeneous landscape at an Arctic tundra site during snowmelt

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Abstract
During snowmelt over a continuous snow cover, the vertical turbulent exchanges of sensible and latent energy are influenced by regional air-mass characteristics, which exert a strong control on air temperature. In high-latitude sites, the melting surface rapidly becomes heterogeneous, with patches of snow and snow-free areas. Local advection occurs when near-surface air layers are warmed due to sensible heal flux from the snow-free areas, with the resulting heat transferred horizontally to adjacent snowpatches. This advection greatly increases the rate of snowmelt along the leading edges of the snowpatches. In order to estimate correctly the average melt rates of the snowpatches and the bulk energy balance of the entire landscape, it is necessary to estimate the local advection component. To date, few studies have dealt with this problem. This paper reports results from an Arctic tundra site located approximately 55 km northeast of Inuvik, Northwest Territories, Canada. The importance of local advection is estimated by comparing the sensible heat flux of the snowpatches to estimates of sensible heat without local advection. This latter term is derived from a relationship between upper air temperature and sensible heat flux over a continuous snow cover. This work has important implications for developing models that correctly represent the cryosphere of tundra regions, and in developing appropriate scaling techniques for heterogeneous landscapes.

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