Surface fluxes of heat and water vapour from sites in the European Arctic

Measurements of the surface fluxes of heat and water vapour were taken at f our sites across the European Arctic as part of the EU funded LAPP project. The sites cover a range of latitudinal, altitudinal and climatic condition s. The most northerly site is near Ny-Angstrom lesund, Svalbard, a polar se mi-desert with continuous permafrost. A second permafrost site is a fen are a in the Zackenberg valley, East Greenland. Finally two sites in northern F inland, Skalluvaara and Kaamanen are on the southern boundary of the region affected by permafrost. At all sites measurements were made of the turbule nt fluxes of heat and water vapour using eddy correlation equipment for at least one active season. The net radiation totals for July and August are similar at all sites. At t he sites with permafrost a substantial proportion (over 20%) of the net rad iation goes into soil heat flux, to thaw the soil moisture in the top metre . Of the remaining energy just over half is used for evaporation. At the Fi nnish sites the vegetation is largely deciduous and this is seen in the rec ord with higher evaporative ratios in July and August, after the vegetation becomes green. The Finnish sites tend to have higher surface resistance to evaporation; ho wever, the evaporative demand is greater leading to slightly higher evapora tion rates. The two Finnish sites have a similar seasonal pattern determine d by the water table and seasonality of the vegetation. The two northern si tes show a pattern that is determined primarily by the variation of water t able only. It is concluded that the water balance through the active season is influenced primarily by the history of snow cover. The seasonality of t he vegetation, the permafrost and the depth of water table, are also import ant influences.