Subsurface ice properties, genesis, and preservation in the Dry Valleys, Antarctica

The presence of subsurface ice is an outstanding problem in the Antarctic Dry Valleys. Current models indicate that ice in soils should sublimate to several meters below the surface within a few thousand years. However, ice is commonly found within the top decimeters in soils that are up to millions of years old. Subsurface ice is important because it is a fundamental component of diverse landscape processes including patterned ground formation (surface renewal, micro-relief generation), downslope soil motion, and pedogenesis. Ice-cemented soils are subject to contraction-expansion as they cool and warm and, as a result they tend to form distinctive polygonal patterns delineated by troughs over thermal contraction cracks. Furthermore, subsurface ice may provide an archive of paleoenvironmental climate, and it can be an important source of water for biological, as well as geomorphic processes. We examine the various forms, characteristics, and mechanisms of the formation of subsurface ice in the Dry Valleys. Data on stable isotope, particulate debris, and ions in the various forms of ice are shown for the various types of ground ice, which include interstitial ice in soils, buried glacial ice, and according recent findings, segregation ice at the lower elevations. Based on vertical profiles of salts and of stable isotope in ice, we have developed a model that explains formation and preservation of ground ice for long periods of time. This is of particular interest in light of previous sublimation models that indicate that the ground ice is not stable, and should disappear relatively quickly due to sublimation. Lessons learned from the Dry Valleys have direct implication for studies of ground ice on Mars.