First measurements of 222Rn and 220Rn activities in soil in Taylor Valley, Antarctica.

Warming global climate threatens the stability of the polar regions and may result in cascading broad impacts. Studies conducted on permafrost in the Arctic regions indicate that these areas may store almost twice the carbon currently present in the atmosphere. Therefore, permafrost thawing has the potential to magnify the warming effect by doubling the more direct anthropogenic impact from burning of fossil fuels, agriculture and changes in land use. . Permafrost thawing may also intensify the Rn transport due to the increase of fluid saturation and permeability of the soil. A detailed study of 222Rn and 220Rn activity levels in polar soils constitutes a starting point to investigate gas migration processes as a function of the thawing permafrost. Although several studies have been carried out in the Arctic regions, there is little data available from the Southern Hemisphere. The Italian - New Zealand "SENECA" project aims to fill this gap and to provide the first evaluations of gas concentrations and emissions from permafrost and/or thawed shallow strata of the Taylor Valley, Antarctica. Taylor Valley is one of the few Antarctic regions that are not covered by ice and therefore is an ideal target for permafrost investigations. Results from our first field observations highlight very low values for 222Rn (mean 621 Bq m-3, max value 1,837 Bq m-3) and higher values for 220Rn (mean 11,270 Bq m-3, max value 27,589 Bq m-3), suggesting a shallow source. These measured activity values are essentially controlled by the radionuclide content in the soil, by the permeability and porosity of the soil, and by the water content. This dataset also represents an important benchmark for future measurements to track the melt progress of Antarctic permafrost.