Two years with extreme and little snowfall: Effects on energy partitioning and surface energy exchange in a high-Arctic tundra ecosystem

Snow cover is one of the key factors controlling Arctic ecosystem functioning and productivity. In this study we assess the impact of strong variability in snow accumulation during 2 subsequent years (2013-2014) on the land-atmosphere interactions and surface energy exchange in two high-Arctic tundra ecosystems (wet fen and dry heath) in Zackenberg, Northeast Greenland. We observed that record-low snow cover during the winter 2012/2013 resulted in a strong response of the heath ecosystem towards low evaporative capacity and substantial surface heat loss by sensible heat fluxes (H) during the subsequent snowmelt period and growing season. Above-average snow accumulation during the winter 2013/2014 promoted summertime ground heat fluxes (G) and latent heat fluxes (LE) at the cost of H. At the fen ecosystem a more muted response of LE, H and G was observed in response to the variability in snow accumulation. Overall, the differences in flux partitioning and in the length of the snowmelt periods and growing seasons during the 2 years had a strong impact on the total accumulation of the surface energy balance components. We suggest that in a changing climate with higher temperature and more precipitation the surface energy balance of this high-Arctic tundra ecosystem may experience a further increase in the variability of energy accumulation, partitioning and redistribution.