ABSTRACT

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.

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