This Small Grant for Exploratory Research explores the use of magnesium isotopes in understanding the preservation of ice in soils from the Dry Valleys of Antarctica. With such little precipitation in the region, this ice should have completely sublimed away, nonetheless there is geologic evidence of ten-million-year-old ice in some areas. Its ubiquitous presence in Dry Valley's soils implies some form of recharge, seemingly incompatible with the low precipitation rates. This project studies the Mg-isotopes found in soluble salts and, by association, water transport. Magnesium isotopes undergo mass dependent fractionation during the volatilization and condensation, and thus offer the possibility to constrain both the water source and other processes by which ice is mobilized. The measurements require the high precision made possible only recently by development of the MC-ICPMS. The method will be applied to Mg-salts extracted from archived Antarctic soils, as well as cores recovered by the 1970s Dry Valley Drilling Project.
In terms of broader impacts, this project would support a graduate student, who would learn cutting edge geochemical techniques while applying them to an exciting earth science question. This work is critical to understanding the environmental record offered by the Dry Valleys, including the deep ice records that may give seven-million year old samples of the earth's atmosphere. The work also has applications to understanding permafrost on Mars and interpreting recent rover observations.
