Identifying the permafrost isotopic signal and assessing permafrost freezing age by radionuclides

We use Radium isotopes to assess the freezing age of the pore-ice water. Because of the effort required to extract sufficient amounts of pore-ice water, and due to the expected low activity (concentration), we use ratios of different Radium isotopes. These ratios can serve as a unique signal of the permafrost, testifying to the presence of thawed permafrost water in the active layer or local streams. The radium isotope 226Ra is the longest-lived of the four naturally-occurring Ra isotopes, with half-life of 1600 years, wich allows the dating of approximately 8,000 years ago. This dating range is appropriate for estimating freezing ages of the Adventdalen area deposits, which are Holocene in age. To achieve the study objectives several core drilling campaigns have already been completed in Adventdalen during spring and summer, and more campaigns are planned. Since Radium is a rare element, several kg's of permafrost soil is needed in order to get enough pore-ice water for analysis. we use a multi-core approach by digging a ditch and hand-drilling 5 to 6 5-cm diameter boreholes next to each other. In the laboratory we separate soil from thawed pore ice and the liquid phase is running through manganese-coated acrylic fibers, radium isotopes activity are detected by the RaDecc (a device that measures the disintegrations of the radium isotopes to radon and polonium). This could provide another perspective on thawing-freezing processes, which may yield insight into permafrost formation models and climate history in circumpolar areas.