Interactions of shrubs and snow in arctic tundra: measurements and models

In arctic tundra, where wind transport of snow is common, shrubs can significantly modify the distribution and physical characteristics of the snow cover. We examined interactions between shrubs and snow by measuring snow depths along three 1-km transects in arctic Alaska and then measuring plant canopy characteristics at the same locations during the following growing season. Snow depths correlated closely with shrub canopy height and stem diameter. Shrubs increased snow depths by 27%, independent of local variations in topographic relief. We also used a snow-transport and energy-balance snowmelt modelling system to perform a series of simulations over a 4 km domain near the field site. A shrub increase was simulated by replacing the current tussock and wet tundra vegetation types with shrub tundra. The shrub expansion increased the domain-averaged snow depth by 20% and decreased blowing-snow sublimation fluxes by 60%. The snow cover change affected the timing and magnitude of all surface energy balance components during the melt, and increased runoff late in the snowmelt period. Shrubs increased snow accumulation by an amount approximately equal to the fraction of the total winter snowfall that is normally lost to sublimation, suggesting that an increase in shrub cover could significantly increase snow depths in the region, even without an increase in precipitation.