Katharine Maher

Stanford University

2015 James B. Macelwane Medal Winner

Paul Cassak, Bethany List Ehlmann, Colette L. Heald, Matt Jackson, and Kate Maher were awarded the 2015 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony, held on 16 December 2015 in San Francisco, Calif. The medal is for “significant contributions to the geophysical sciences by an outstanding early career scientist.”


Kate Maher has made extraordinary contributions to our understanding of the geochemistry of critical zone processes. Her achievements have impacted our understanding of silicate weathering, soil formation, groundwater flow and transport, and the global carbon dioxide cycle.

Kate’s research specifically focuses on the rates of chemical reactions that occur at Earth’s surface and down to shallow depths. She has used her expertise in isotope geochemistry and reactive transport modeling to understand how water moves through rock materials, transforming it chemically. Her insightful analysis of how to interpret the disequilibrium of uranium isotopes is informing the interpretation of erosion and soil production.

Her impactful work began during her graduate work at Berkeley and has developed into a more generalized use of isotope systematics in hydrologic systems during her tenure at Stanford. She and her students are now bridging the divide between hydrological and geochemical modeling to push forward the understanding of flow and transport in soils, aquifers, and deeper reservoirs. Geochemical measurements hold the promise of constraining hydrologic modeling at a variety of spatial and temporal scales, and Kate’s work is pushing forward this frontier both from a theoretical point of view and in application to real systems.

Her models and data have elucidated several -long-​-standing puzzles. She clarified one of the main reasons why the kinetics of reactions are observed to be slower in the laboratory than the field. She presented quantitative models explaining paradoxes related to solutes and stream flow in catchments. Her latest work is elucidating the thermostat for the global carbon cycle. At the same time, she is contributing to more applied problems related to the geological sequestration of carbon dioxide and radionuclides in the environment.

Kate has the quantitative skills, geological insights, and leadership talent needed to tackle the biggest problems in Earth surface processes. We currently know more about modeling the movements of air masses and ocean waters globally than we know about modeling the movements of water, solutes, and particles in the highly heterogeneous critical zone. Kate will be at the forefront as we evolve in our understanding of this frontier.

—Susan L. Brantley, Pennsylvania State University, University Park


Thank you, Sue, for your generous citation and for your support and encouragement over the years. You have been a role model for so many young scientists, and on behalf of all of us, I thank you for the myriad roles that you have played in our careers.

It is a tremendous honor to receive the James B. Macelwane
medal, and I thank AGU, the nominations committee, and my nominators for creating this special moment that I will cherish for the remainder of my career.

I have had the good fortune to stand on the shoulders of several giants in my field. First, I would like to acknowledge my Ph.D. adviser, Don DePaolo of the University of California, Berkeley, whose infinite understanding of Earth processes and unique ability to envision even the most complex as simple “chemical reactors” have always challenged me to evaluate the most simple case first as it is often where the central challenges become apparent. I would also like to thank Carl Steefel at Lawrence Berkeley National Laboratory for his ceaseless patience in converting an engineer into a geochemical modeler and for leading me into the field of reactive transport. I would also like to thank the U.S. Geological Survey Mendenhall program and Jennifer Harden, Art White, and David Miller for introducing me to the fascinating world of soils.

At Stanford University, I encountered another cast of giants who have offered new shoulders and new views. I chose Professor Gordon Brown as my faculty mentor, hoping he would be honest and fair in providing feedback. This turned out to be quite an underestimate. Gordon not only introduced me to the beautiful world of surface chemistry but provided boundless advice, as well a few prescient nudges. I could not imagine a better mentor. Dennis Bird, Page Chamberlain, and Scott Fendorf at Stanford have also been outstanding mentors and teachers, as have the many postdocs, students, and staff who have crossed paths with our research group. The latter are too numerous to name; however, I am sincerely grateful to all of them for their intelligence, spirited natures, and hard work.

Finally, I wish to thank my family for their patience, encouragement, and support. My mother, Celia Kathleen (CK), has always been my anchor, and without her I could not have become a geoscientist. My husband, Matthew, is a true giant upon whose shoulders I stand every day.

—Katharine Maher, Stanford University, Stanford, Calif.