Collaborative Research: Subglacial Water Intrusion in Greenland

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。要充分了解冰盖的流动和动态，需要了解其冰下界面的状态。虽然格陵兰冰盖床的地形已通过无线电回声探测进行了研究，但其融化和冻结状态（这本身会影响其未来的演变）是从数值模型而不是直接证据中推断出来的。该项目用于分析PARCA和CReSIS计划下收集的现有雷达回波数据，目的是提供格陵兰冰下水范围的直接证据，并为冰川学界提供其范围的地图。先前的回波分析已经发现接收信号的可变性太大而不能提取由于床材料的变化而引起的分量。现在，一种基于对无线电回波信号强度的进一步分析的方法已经被开发、验证和报告，该方法允许可靠地确定床的状态。这项工作将把这种方法应用于所有现有的无线电回波数据，以生成整个格陵兰岛基底融化程度的地图。该程序依赖于对冰盖床的无线电回波进行比以前更精确的评估。它允许减少回波强度的变化，并检测床料的变化。它已被测试的数据从格陵兰岛上空的一些航班在1999年的字段季节，并验证了测试的自我一致性，回波强度统计，界面平滑度，和测量表面和界面斜率之间的关系。该小组将处理1998年至2005年期间飞行的数据。将应用适当的自洽性和统计特性检验。将在整个过程中确定是否存在水。将对结果进行解释，并编制地图说明这些结果。每个主要水景的连续性和地形背景将被调查和比较。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).A full understanding of the flow and dynamics of an ice sheet will require knowledge of the state of its subglacial interface. While the topography of the Greenland Ice Sheet bed has been studied by radio echo sounding, its state in terms of melting and freezing, which itself affects its future evolution, has been inferred from numerical models, rather than from direct evidence.This project is for analysis of existing radar echo data gathered under the PARCA and CReSIS programs, with the objective of generating direct evidence of the extent of subglacial water in Greenland and providing the glaciological community with maps of its extent. Previous echo analysis has found the variability of the received signal too great to extract the component due to variation of the bed material. Now, a method has been developed, validated and reported, based on further analysis of radio echo signal intensities, which allows the state of the bed to be determined reliably. This work will apply this method to all the available radio echo data, to generate maps of the extent of basal melting throughout Greenland. The procedure relies on a more precise assessment of radio echoes from the bed of the ice sheet than has previously been provided. It allows the variability of echo intensity to be reduced, and the variation of the bed material to be detected. It has been tested with data from a number of flights over Greenland during the 1999 field season, and is validated by tests of self-consistency, of echo intensity statistics, of interface smoothness, and of the relation between measured surface and interface slopes. The team will process data from flights undertaken between 1998 and 2005. Appropriate tests of self-consistency and statistical behavior will be applied.The presence or absence of water will be determined throughout. Results will be interpreted and maps compiled illustrating these results. The continuity and topographical context of each major water feature will be investigated and compared.