Thermal Regime and Properties of Soils and Ice-Rich Permafrost in Beacon Valley, Antarctica

Abstract

Subsurface temperatures in polar environments control geomorphic, hydrologic, and biologic processes and ground ice stability. Most studies of the thermal regime in permafrost areas have been developed for the Arctic where interest and concern focus on permafrost thawing. In contrast, this study focuses on soils in the McMurdo Dry Valleys of Antarctica where conditions are much colder and drier, and long-term persistence of ground ice is of interest including as an analog site for Mars. The soil temperature in Beacon Valley, one of the McMurdo Dry Valleys, has been modeled using the surface temperature, measured heat capacity, and temperature-dependent thermal conductivity and compared to continuous, high-resolution measurements of temperatures for a decade down to 19.6-m depth. For the temperature range of −47.9 to 7.5 °C at our study site, the heat capacity of the dry soil ranges from 580 to 690 J · kg−1 · K−1, thermal conductivity from 0.22 to 0.27 W · m−1 · K−1, and the calculated thermal diffusivity from 0.23 to 0.25 mm2/s. Both the finite difference method and the finite volume method are used to solve the 1-D heat diffusion equation; the finite volume method-modeled temperature most closely approximates the measured temperature at all depths with average differences ranging from 0.01 to 0.03 °C. The latent heat contribution of documented episodic snowmelt events and of modeled changes in ice content due to condensation or sublimation is negligible. This study can be applied readily to thermal regimes of similar systems where subsurface temperature measurements are not available such as on Mars.