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

在许多复杂的动力系统中都可以观察到有序从无序中出现的现象。一些地质特征，包括有图案的地面，构成了自然界中一些最清晰和最容易理解的非生物自组织的例子。提出了一种结合现场测量和计算机模拟冻融活动下土壤中离散颗粒运动的协调方案来研究图案地面的自发出现和动态。这两种方法的紧密结合有望产生协同效应，通过模拟指导研究，在该领域制定新颖和更精确的问题，反之亦然。通过以下具体目标的整合，将获得一个新的和更基本的关于模式地面作为自组织的主要例子的观点：(1)建立一个反复冻融的土壤中离散颗粒运动的三维计算机模拟，并用它来研究冻土模式的发展；(2)在分选良好的圈层和条纹研究点，测量石质和土壤的位移，记录模式的形成及其对扰动的反应，并利用自动化仪器监测土壤温度、湿度和气候参数；(3)通过计算机模拟和室内实验，构建了图案地面分选的微观力学模型；(4)建立一个真实的传热传质模型，研究分选圈形成的关键因素：活动层深度和传播冻融锋的三维几何形状。开发一个现实的冻土近地表传热模型的一个重要的实际好处是，它有望有助于更精确地理解气候变化对永久冻土层的预期影响，以及永久冻土层温度中包含的近期气候变化的记录。拟议研究的目标是了解北极地区这些石头圈等图案从无序初始状态产生的过程：在这种情况下，一个被1-2米的各种海滩沉积物覆盖的波浪切割平台。

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 permafro st 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.