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

合作研究：冰中微物理过程的织物和纹理特征

• 批准号: 0135989
• 负责人: Larry Wilen
• 金额: --
• 依托单位: Ohio University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-03-15 至 2007-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0135989&HistoricalAwards=false
• 关键词: Collaborative; Research; Fabric; Texture; Characteristics

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.

0135989 Wilen这是华盛顿大学和俄亥俄州大学的主要研究人员的合作提案。冰的微观结构和它的变形之间的相互作用的详细知识是需要评估地层分层的完整性和冰芯中的深度-年龄关系，这是解释古气候记录的必要条件。主要研究人员将利用微观结构来研究结构，晶体c轴的取向分布，以及纹理，晶体的大小和形状。冰变形的数值模拟是理解这些相互作用的有用工具。冰变形的精确建模是复杂的因素，如组构，粒度，动态重结晶，应力水平，和初始条件的精确知识。例如，冰的结构随着冰的应变而演变，变形取决于结构。必须理解这种复杂的反馈机制，才能正确模拟冰的变形。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，但有很好的例子，近表面冰的冰芯，显然不是各向同性的。要计算冰盖的变形速率，必须知道初始结构。Wilen博士将联合收割机的新的自动结构分析仪（AFA）的结果与详细的冰变形模型（Thorsteinsson博士）的预测相结合，以完善和更好地约束这些模型。AFA在薄切片中提供了新的信息，因为测量的c轴方向的精度和数量大大提高。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，以解决有关近地表结构，变形机制，动态重结晶和层扰动的潜在来源的问题。这些数据将用于约束组构演化和再结晶过程的模型。有了更精确的模型，科学家们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）和格陵兰冰盖项目2（GISP 2）冰芯上90%的气候记录之间的一致性，以及下10%的分歧强调需要了解和预测这些和未来深冰芯的破坏机制和可能深度。有证据表明，地层扰动是由冰晶在不同尺度上的各向异性性质引起的。为了正确模拟各向异性冰的变形，必须了解组构对变形的影响。