Kristel Chanard has improved our understanding of the role of hydrology in Earth’s space- and time-dependent deformation, gravity field, and rheology. In that endeavor, Kristel’s research has been very much influenced by and followed up on some of John Wahr’s own research. Kristel is exploring how Earth deforms through the development and intelligent use of space geodetic data. The analyses and discussions in her papers are full of interesting points, careful consideration of caveats and related work, and convincing argumentation. She always matches a rigorous observational component in her papers with intriguing and innovative analysis and interpretation. For example, Kristel integrated GPS time series with time-dependent GRACE satellite gravity data from across the India-Tibet collision zone to demonstrate that seasonal hydrological loading variations produce notable annual deformation cycles in both vertical and horizontal components. Importantly, Kristel was able to show that models of the layered elastic Earth structure can be improved by optimizing the fit to phase and amplitude of both vertical and horizontal deformation data. Later, Kristel expanded this approach to the whole Earth, considering nearly 700 GPS stations and complete GRACE gravity data sets. This analysis reconciles the complete 4D surface deformation field and gravity time series through a global elastic spherical and layered Earth model incorporating seasonal elastic deformation and geocenter motion. Finally, she presented a completely new way to examine deep-Earth rheology using geodetic data sets, by developing an approach to estimate short-term asthenospheric viscosity revealed by deformation–gravity phase relations in the seasonal load deformation of Earth. This first analysis of its kind could only provide a lower bound on a global average of short-term asthenospheric viscosity, but opened a whole new window into the workings of the deep Earth. In recent years, Kristel has continued to make valuable contributions at an accelerating pace, including additional studies of seasonal load deformation and seismicity modulations, papers on statistical analyses of seismicity modulation by periodic stresses ranging from tidal to seasonal frequencies, and investigations of Earth orientation parameters and Earth center representations. Kristel has also made impactful contributions to the International Terrestrial Reference Frame, to the rapidly growing field of hydrogeodesy, and to improved understanding of fault zone properties and slip behaviors. Kristel will surely continue to make more insightful contributions to our knowledge of the shape and deformation of Earth.

—Roland Bürgmann, University of California, Berkeley

I am deeply humbled and honored to be one of this year’s recipients of the John Wahr Early Career Award, among so many deserving scientists. This recognition holds great significance, as John Wahr’s career has been an inspiration for me. His groundbreaking work in understanding Earth’s deformation in response to hydrological changes, from theoretical developments to pioneer satellite observations, has paved the way for my own research endeavors. Moreover, Wahr’s dedication to teaching and mentoring has had a profound impact on the geodetic community, shaping the careers of generations of scientists. I would like to thank everyone who helped with my nomination to this award, particularly my nominator, Roland Bürgmann, and tell them I hope to follow in the esteemed footsteps of John Wahr. Thanks to the collective efforts of the geodetic community, we are now witnessing an explosion of new satellite observations. These observations provide us with unprecedented tools to address crucial scientific questions and pressing societal challenges. From unraveling the solid Earth’s rheological properties to monitoring the climate variables, I am passionate about exploring various, yet interconnected, research domains. My broad curiosity in the Earth sciences, along with my research values, has been largely inspired by three outstanding scientists: Luce Fleitout, Alexandre Schubnel, and Jean-Philippe Avouac. Their support, guidance, generosity in time, and ideas have been instrumental in shaping my research trajectory. I aspire to meet the impact they have had on young scientists like myself. I am also deeply grateful to all my collaborators for continuously teaching me new things and making this career extremely enjoyable. In particular, I thank those involved in the International Terrestrial Reference Frame realization, for warmly welcoming me into their community a few years ago and guiding me into the intriguing world of geodesy. I extend my gratitude to the exceptional students and postdocs I have had the privilege to work with. Their enthusiasm, dedication, and innovative thinking have made my career rewarding. I am immensely proud of their achievements and look forward to witnessing their future work and success. Last, I thank all members of our community advocating for diversity, equity, and inclusion in our field. Their commitment to creating a more inclusive environment has had a profound impact on my career, and I hope our collective efforts will shape an even more inclusive community in the future. —Kristel Chanard, Institut de Physique du Globe de Paris