Collaborative Research: Fabric and Texture Characteristics of Micro-Physical Processes in Ice

这是华盛顿大学和俄亥俄大学的主要研究人员合作提出的一项建议。为了评估地层分层的完整性和冰芯的深度-年龄关系，需要详细了解冰的微观结构及其变形之间的相互作用，这对解释古气候记录至关重要。首席研究员将使用微观结构来研究织物，晶体c轴的方向分布，以及晶体的纹理，大小和形状。冰变形的数值模拟是理解这些相互作用的有用工具。由于结构、晶粒尺寸、动态再结晶、应力水平和对初始条件的精确了解等因素，冰变形的精确建模变得复杂。例如，冰织物随着冰的拉伸而演变，变形取决于织物。要正确地模拟冰的变形，必须了解这种复杂的反馈机制。在另一个例子中，通常的假设是初始结构是各向同性或随机的，但在冰芯中有很好的近表面冰的例子，显然不是各向同性的。要计算冰原的变形速率，必须知道冰原的初始结构。Wilen博士将把他的新自动织物分析仪（AFA）的结果与详细的冰变形模型的预测（Thorsteinsson博士）结合起来，以改进和更好地约束这些模型。由于测量c轴方向的精度和数量大大提高，AFA在薄片中提供了新的信息。主要研究人员将分析现有数据，并从冰芯中收集有关结构和纹理的新数据，以解决有关近表面结构、变形机制、动态再结晶和层扰动的潜在来源的问题。这些数据将用于约束织物演化和再结晶过程的模型。有了更精确的模型，科学家可以解决与冰变形和冰芯有关的不同问题和重要问题。例如，最近格陵兰冰芯项目（GRIP）和格陵兰冰盖计划2 （GISP2）的上90%冰芯的气候记录一致，而下10%的气候记录不一致，这强调了了解和预测这些和未来深层冰芯的机制和可能的破坏深度的必要性。有证据表明，地层扰动是由不同尺度冰晶的各向异性引起的。为了正确地模拟各向异性冰的变形，必须了解织物对变形的影响。

0135989WilenThis is a collaborative proposal by Principal Investigators at the University of Washington and Ohio University. Detailed knowledge about the interactions between micro-structure of ice and its deformation is needed to assess the integrity of stratigraphic layering and the depth-age relationship in ice cores, which is essential for interpreting the paleoclimate record. The Principal Investigators will use micro-structure to study fabric, the orientation distribution of crystal c-axes, and texture, the size and shape of crystals. Numerical modeling of ice deformation is a useful tool in understanding these interactions. Accurate modeling of ice deformation is complicated by factors, such as the fabric, grain size, dynamic recrystallization, stress level, and precise knowledge of initial conditions. For example, ice fabric evolves as the ice is strained and the deformation depends on the fabric. This complicated feedback mechanism must be understood to correctly model ice deformation. In another example, the usual assumption is that the initial fabric is isotropic or random, but there are excellent examples of near-surface ice in the ice cores that are apparently not isotropic. One must know the initial fabric to calculate the deformation rate in ice sheets. Dr. Wilen will combine results of his new automatic fabric analyzer (AFA) with predictions of detailed ice deformation models (Dr. Thorsteinsson) to refine and better constrain such models. The AFA gives new information in thin sections because the precision and number of measured c-axis orientations are greatly improved. The Principal Investigators will analyze existing data and collect new data on fabric and texture from ice cores to address questions regarding near-surface fabric, deformation mechanisms, dynamic recrystallization, and potential sources of layer disturbances. The data will be used to constrain models of fabric evolution and recrystallization processes. With the more refined models, scientists can address different questions and important problems related to ice deformation and ice cores. For example, the recent agreement between the climate records from the Greenland Ice Core Project (GRIP) and Greenland Ice Sheet Project 2 (GISP2) ice cores of the upper-90%, and the disagreement in the lower-10% emphasizes the need to understand and predict the mechanisms and probable depths of disruption in these and future deep ice cores. Evidence suggests that the stratigraphic disturbances arise from the anisotropic nature of ice crystals at a variety of scales. To properly model the deformation of anisotropic ice, the influence of fabric on deformation must be well known.