Anisotropic sea ice mechanics in the Arctic

由于全球变暖，北极和南极的冰盖正在发生变化，北极海冰的夏季范围显著减少。最近观测到的北极海冰的迅速减少，甚至比最悲观的气候模式的预测更为极端，这表明这些模式没有充分呈现控制海冰减少的过程。卫星观测、野外工作和模拟都指出海冰动力学在控制北极海冰质量平衡方面的重要性。海冰动力学中最大的不确定性在于海冰内部应力与海冰覆盖变形和状态之间的关系，即海冰流变学。现有气候模式对海冰流变的描述将冰盖视为各向同性，因此在给定位置，在所有方向上都有相同的破坏阻力。然而，十多年来，人们已经知道冰盖具有高度的各向异性，在所有长度尺度上都存在定向裂缝，这些裂缝控制着优先变形的方向。虽然研究人员已经意识到各向异性力学的重要性，但直到最近才建立了各向异性流变学模型，并将其纳入气候模型的海冰成分。该项目旨在通过结合最近制作的高分辨率卫星变形图和计算机建模，消除控制各向异性产生和破坏过程中的基本不确定性。该研究的一个主要成果将是将各向异性海冰流变学的新表示纳入CICE海冰模型，该模型是许多气候模式中使用的海冰模型，包括英国哈德利中心系列气候模式。我们将使用CICE来研究各向异性流变学在最近和快速减少北极海冰中的作用。

In response to global warming, the ice covers of the Arctic and Antarctic are changing, with a significant reduction in the summer extent of Arctic sea ice. The observed recent, rapid reduction of Arctic sea ice is more extreme than the predictions of even the most pessimistic of climate models, which suggests that these models do not present the processes controlling the reduction of sea ice adequately. Satellite observations, field work, and modelling all point to the importance of sea ice dynamics in controlling the mass balance of Arctic sea ice. The greatest uncertainty in sea ice dynamics is in the relationship between internal sea ice stresses and the deformation and state of the sea ice cover, known as the sea ice rheology.The description of sea ice rheology in existing climate models treats the ice cover as isotropic, so that at a given location there is equal resistance to failure in all directions. However, it has been known for over a decade that the ice cover is highly anisotropic, with oriented cracks present at all length scales, and these cracks control the directions of preferential deformation. While researchers have been aware of the importance of anisotropic mechanics, only recently has a model of anisotropic rheology been constructed and incorporated into the sea ice component of a climate model. This project aims to eliminate fundamental uncertainty in the processes controlling anisotropy creation and destruction through a combination of recently produced, high-resolution satellite deformation maps and computer modelling. A major result of the research will be a new representation of anisotropic sea ice rheology incorporated into the CICE sea ice model, which is the sea ice model used in many climate models, including the UK Hadley Centre series of climate models. We will use CICE to investigate the role of anisotropic rheology in producing the recent and rapid reduction of Arctic sea ice.