A model for sorted patterned ground shows that some types arise from density-driven Rayleigh free convection during thawing of water-saturated recurrently frozen soils. The regularly spaced convection cells result in an uneven melting of the underlying ice front. Frost action causes stones to be upthrusted and to form in a pattern on the ground surface that mirrors the corrugation in the underlying ice front. This award supports field work, laboratory experiments, and modeling studies focused on obtaining pattern width-to-depth ratios for underwater polygons. These will be supported by laboratory studies of underwater polygons. A novel feature of the field and laboratory studies is the use of infrared thermography to detect the free convection flows which precede any visible patterning. Modeling studies will support these experimental investigations of sorted polygons. Modeling studies will also be pursued to determine the differential thaw penetration due to the heat transfer associated with free convection in the active layer.
