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

从无序到有序的现象在许多复杂的动力系统中都能观察到。一些地质特征，包括有图案的地面，构成了自然界中最明显和最容易获得的非生物自组织的例子。提出通过冻融作用下土壤中离散颗粒运动的野外测量和计算机模拟相结合的程序来研究花纹地面的自发产生和动力学。这两种方法的紧密结合有望起到协同作用，模拟将指导研究在该领域提出新的和更精确的问题，反之亦然。通过整合以下具体目标，将获得一个新的、更基本的观点，即花纹地面是自组织的主要例子：(1)开发反复冻融作用下离散颗粒在土壤中运动的三维计算机模拟，并用它来研究冻土中花纹的发展；(2)测量石块和土壤的位移，记录花纹的形成及其对干扰的反应，并利用自动化仪器监测已建立的研究场地的土壤温度、水分和气候参数，这些场地具有发达的分类圆圈和条纹；(3)通过计算机模拟和实验室实验，建立了花纹地面分选的微观力学模型；(4)发展了一个真实的热质传输模型，研究了影响分选圆圈形成的关键因素：活跃层深度和冻融前沿传播的三维几何形状。为冻土开发一个现实的近地表热传递模型的一个重要的实际好处是，它有望有助于更准确地理解气候变化对多年冻土区的预期影响，以及包含在永久冻土温度中的最近气候变化的记录。拟议研究的目标是了解北极的这些石圈图案是如何从无序的初始状态产生的：在这种情况下，波浪切割平台覆盖着1-2米各种海滩沉积物。

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.