CAREER: Inversion of Localized High-Resolution Polar Gravity Fields to Estimate Mass Change

自2002年以来，GRACE系列卫星任务一直在测量地球变化的重力场。这些观测发现了现今冰盖和冰川中的冰损失。冰的损失在决定世纪海平面上升方面起着关键作用，海平面上升威胁着生活在沿海地区的数亿人。改进对今天冰在何处何时消失的观测是改进对未来冰和海平面变化估计的关键。这些估计数对于评估相应的风险和实施缓解政策至关重要。在这里，研究人员开发和测试新的工具，以改善卫星测量重力，特别是在极地地区。这些最新发展提高了卫星观测的空间和时间分辨率。 它们使人们能够更好地了解冰盖和冰川如何在物理上对不断变化的气候条件作出反应，特别是在区域范围内，这是一个悬而未决的科学问题。该项目还向亚利桑那大学的研究生和本科生提供了地球物理学和遥感方面的支助和培训。 它的教育方面，与研究相结合，在课堂环境和研究实验室环境中进行。目前全球卫星重力数据产品的空间分辨率在极地地区受到其构造方式的根本限制。在这里，该团队使用空间光谱定位技术，直接从卫星高度的现场测量中构建仅极性时变重力场。这些极地重力场大大提高了全球产品的空间和时间分辨率。本文利用贝叶斯反演方法分析了与21世纪海平面上升有关的两个问题：1）利用贝叶斯反演方法约束劳伦泰德冰盖在末次盛冰期的厚度和形状; 2）结合格陵兰GPS地表位移，研究冰的质量变化是如何在固体地球表面运动中表达的。该奖项反映了NSF的法定使命，并被认为值得支持通过使用基金会的知识价值和更广泛的影响审查标准进行评估。

The GRACE series of satellite missions have been making measurements of Earth’s changing gravity field since 2002. These observations detect present day ice loss in ice sheets and glaciers. The ice loss plays a key role in determining 21st century sea level rise, which threatens hundreds of millions of people living in coastal regions. Improving observations of where and when ice is being lost today is key for improving estimates of future ice and sea level change. These estimates are critical to assess the corresponding risks and implement mitigation policies. Here the researchers develop and test new tools to improve satellite measurements of gravity, specifically in the polar regions. These state-of-the-art developments improve the spatial and temporal resolution of satellite observations. They allow a better understanding of how ice sheets and glaciers physically respond to changing climatic conditions, notably at the regional scale, an outstanding scientific question. The project also provides support and training in geophysics and remote sensing to graduate and undergraduate students at the University of Arizona. Its educational aspects, integrated with the research, are carried out both in a classroom setting and research-lab setting. Specific efforts are geared toward including students from underrepresented groups in STEM.Current global satellite gravity data products have spatial resolution that is fundamentally limited in polar regions by how they are constructed. Here the team uses spatio-spectral localization techniques to construct polar-only time-variable gravity fields directly from the in-situ measurements at satellite altitude. These polar gravity fields significantly improve spatial and temporal resolution over global products. They are here used to analyze two problems relevant to 21st century sea level rise: 1) to constrain the thickness and shape of the Laurentide Ice Sheet at last glacial maximum using a Bayesian inversion procedure; 2) combined with GPS surface displacements in Greenland, to investigate how ice mass change is expressed in solid Earth surface motion.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.