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

Abstract

The annually thawing active layer of permafrost is central to considerations of climate change consequences in arctic areas and interpretations of deep permafrost temperatures that constitute and exceptional archive of past climate change. Moreover, a sound understanding of the thermal regime of the active layer is of great interest, because all chemical, biological and physical processes are concentrated there. The author studied this layer by examining the soil physical properties and heat transfer processes that dictate soil temperatures for an arctic desert site in northwestern Spitsbergen. A wide array of soil physical properties based on field observations and laboratory measurements were defined. These include mineralogy, grain size distribution, local regolith thickness, porosity, density, typical soil moisture profile, heat capacity and thermal conductivity. Heat transfer processes were studied through modeling of soil temperatures. The heat transfer model accounted for much of the observed soil thermal regime. It was found that thermal conduction, phase change of soil water at 0°C, and changes 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 the energy budget, causes abrupt warming events and delivers considerable energy to the soil in late spring. An increase in frequency or magnitude of infiltration events could mimic simple spring time surface warming. Advection of ground water and soil internal evaporation were found to be generally unimportant at the site studied.