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，就需要了解其冰下界面的状态。虽然已经通过无线电回波探测研究了格陵兰冰盖床的地形，但其融化和结冰的状态是从数值模型而不是直接证据中推断出来的，这本身就会影响其未来的演变。该项目是为了分析根据PARCA和CReSIS计划收集的现有雷达回波数据，目的是产生格陵兰冰下水范围的直接证据，并向冰川学社区提供其范围的地图。以前的回波分析发现，由于床层材料的变化，接收信号的变异性太大，无法提取分量。现在，基于对无线回波信号强度的进一步分析，已经开发、验证和报告了一种方法，该方法可以可靠地确定床的状态。这项工作将把这种方法应用于所有可用的无线电回波数据，以生成整个格陵兰基底部融化程度的地图。这一过程依赖于对来自冰盖床的无线电回波的更准确的评估，而不是以前提供的评估。它可以降低回波强度的变异性，并检测床料的变化。它已经用1999年野外季节格陵兰岛上空的一些飞行数据进行了检验，并通过自我一致性、回波强度统计、界面平整度以及测量的表面和界面斜率之间的关系的检验得到了验证。该小组将处理1998至2005年间飞行的数据。将应用适当的自我一致性和统计行为测试。水的存在或不存在将在整个过程中确定。将对结果进行解释，并编制说明这些结果的地图。将调查和比较每一主要水域特征的连续性和地形背景。

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.