An Integrated Modeling and Experimental Study of the Formation and Dynamics of Patterned Ground

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The emergence of order from disorder is observed in a wide range of complex dynamical systems. Several geological features, including patterned ground, constitute some of the clearest and most accessible examples of abiotic self-organization in nature. It is proposed to investigate the spontaneous emergence and dynamics of patterned ground through a coordinated program of field measurement and computer simulation of discrete particle motion in soil subjected to freeze/thaw activity. The close bending of these two approaches promises to be synergistic, with the simulations guiding the investigations in formulating novel and more precise questions in the filed and vice-versa. A new and more fundamental view of patterned ground as a prime example of self-organization will be obtained through the integration of the following specific objectives: (1) to develop a three-dimensional computer simulation of discrete particle motion in soil subjected to recurrent freezing and thawing, and use it to investigate the development of patterns in frozen ground; (2) to measure stone and soil displacements, document the formation of patterns and their reaction to disturbances, and monitor with automated instrumentation soil temperature, moisture and climate parameters in established study sites with well developed sorted circles and stripes; (3) to construct a micro-mechanical model of sorting in patterned ground through computer simulation and laboratory experimentation; and (4) to develop a realistic heat and mass transfer model to investigate factors critical in the formation of sorted circles: active layer depth and three-dimensional geometry of propagating freezing and thawing fronts. An important practical benefit of developing a realistic near-surface heat transfer model for frozen ground is that it promises to contribute to a more precise understanding of both the anticipated impacts of climate change permafrost areas, and the record of recent climate change that is contained in permafrost temperatures. The goal of the proposed research is to understand the processes through which patterns such as these circles of stones in the Arctic arise from a disordered initial state: in this case, a wave cut platform covered with 1-2 m of assorted beach sediments.