Soil thermal properties and heat transfer processes near Ny-Alesund, northwestern Spitsbergen, Svalbard

The annually thawing active layer of permafrost is central to consideration s of climate change consequences in arctic areas and interpretations of dee p permafrost temperatures that constitute an exceptional archive of past cl imate change. Moreover, a sound understanding of the thermal regime of the active layer is of great interest, because all chemical, biological and phy sical processes are concentrated there. The author studied this layer by ex amining the soil physical properties and heat transfer processes that dicta te soil temperatures for an arctic desert site in northwestern Spitsbergen. A wide array of soil physical properties based on field observations and l aboratory measurements were defined. These include mineralogy, grain size d istribution, local regolith thickness, porosity, density, typical soil mois ture profile, heat capacity and thermal conductivity. Heat transfer process es were studied through modeling of soil temperatures, The heat transfer mo del accounted for much of the observed soil thermal regime. It was found th at thermal conduction, phase change of soil water at 0 degrees C, and chang es in unfrozen water content are the primary thermal processes that explain the observed soil temperatures in this field site. Melt-water infiltration , which is often overlooked in dw energy budget, causes abrupt warming even ts and delivers considerable energy to the soil in late spring. An increase in frequency or magnitude of infiltration events could mimic simple spring rime surface warming. Advection of ground water and soil internal evaporat ion were found to be generally unimportant at the site studied.