Scale invariance of sea ice deformation: identifying how boundary conditions define the spatial ranges of these relationships

这项工作的目标是确定物理机制控制海冰变形的冬季博福特和楚科奇海。海冰在风和洋流的影响下移动。冰袋在不断地运动，由于它很脆，裂缝。裂缝变成了铅，形成了断裂模式，随着天气的变化而重新组织。在断裂处，冰层剪切，打开和关闭，并显示脊。此外，浮冰变形遵循脆性材料常见的特定关系。例如，裂缝的尺寸遵循这样的关系，其中尺寸的分布不随它们被测量的分辨率而改变。这被称为尺度不变性。我们还看到了浮冰变形的其他紧急行为，在表面应力和海岸边界约束的影响下，冰作为粒状或脆性塑性体。我们将研究在哪些尺度上变形是尺度不变的，以及冰盖如何响应风和冰盖的季节性变化。我们的项目对这一问题的洞察力将改善气候和预测中的海冰漂移和变形建模。这反过来又将改善北极海洋作业的风险评估和减灾工作。它也将允许现实的污染物扩散模拟响应潜在的环境灾害，如石油泄漏，可能成为uncontainable. We的目的是解决一个争论海冰内部应力场是否是各向异性或各向同性，以及是否海冰显示不同的塑性行为在一个范围内的尺度，确定在哪些尺度上的变形是尺度不变的。我们将研究边界条件和强迫在限制海冰变形中的作用，其尺度包括北极海盆、天气和亚中尺度（铅和裂缝的间距）。以下的证据在天气和次中尺度之间的变形控制的物理机制的过渡，我们将确定这是如何涉及到自组织的骨折内的冰袋。我们的假设是：大尺度变形受冰层的几何形状和表面作用力、风和洋流的控制;变形的分形标度中的明显转变与限定较大尺度断裂之间的冰板块的作用力和边界条件的变化有关;应变减弱沿着这些板块边界导致较小尺度的冰应力，其受作用力和冰强度的局部不均匀性的控制;当充填体从封闭固结向无封闭粒状发展时，变形的比例变化存在季节性的过渡。测试这些假设将通过观察指导建模，使用离散元方法模型的机械行为的浮冰。控制连续模型的比较实验将验证特定的流变模型是否适用于各种尺度的海冰。我们希望能够识别出具有更好的海冰漂移、铅开口和海冰扩散代表性的模型。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this work is to identify physical mechanisms controlling sea ice deformation in the winter Beaufort and Chukchi Seas. Sea ice moves under the influence of winds and ocean currents. The ice pack is in constant motion, and as it is brittle, cracks. Cracks open into leads, which form fracture patterns that reorganize with changes in the weather. At fractures, the ice pack shears, opens and closes, and displays ridging. Moreover, the pack ice deformation follow particular relationships common to brittle materials. For example, the size of fractures follow a relationship where the distribution of sizes do not change with the resolution they are measured over. This is termed scale invariance. We also see other emergent behavior of pack ice deformation, with the ice acting as a granular or brittle plastic under the influence of the surface stresses and coastal boundary constraints. We will investigate over which scales that deformation is scale invariant and how the ice pack responds to wind and seasonal changes in ice cover. The insight our project brings to this problem will result in improvements to modeling sea ice drift and deformation in climate and forecasting. This in turn will improve risk assessment and hazard mitigation for Arctic marine operations. It will also allow realistic contaminant dispersion modeling for response to potential environmental disasters such as an oil spill that could become uncontainable.Our aim is to settle a debate on whether the sea ice internal stress field is anisotropic or isotropic, and whether sea ice displays different plastic behavior over a range of scales, identifying over which scales that deformation is scale invariant. We will investigate the role of boundary conditions and forcing in confining sea ice deformation on scales covering the Arctic Basin, synoptic, and submeso- scale (the spacing of leads and cracks). Following evidence for a transition in the physical mechanism controlling deformation between the synoptic and sub-mesoscale, we will identify how this relates to self-organization of fractures within the ice pack. Our hypotheses are: large-scale deformation is controlled by geometry of the ice pack and surface forcing, winds and ocean currents; apparent transitions in the fractal scaling of deformation are related to changes in the forcing and boundary conditions defining plates of ice between the larger scale fractures; strain weakening along these plate boundaries result in smaller scale ice stress controlled by local heterogeneity in forcing and ice strength; and there is a seasonal transition in scaling of deformation as the pack evolves from confined and consolidated to unconfined and granular. Testing these hypotheses will be through observation directed modeling, using a discrete element method model of the mechanical behavior of pack ice. Controlled comparison experiments with continuum models will verify if particular rheological models are appropriate for sea ice across a variety of scales. We expect to identify models with improved representation of sea ice drift, lead opening and sea ice dispersion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.