Steven J. Davis, Walter Immerzeel, Isaac Santos, Drew Turner, and Caroline C. Ummenhofer were awarded the 2018 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony on 12 December 2018 in Washington, D. C. The medal is for “significant contributions to the geophysical sciences by an outstanding early career scientist.”  

Caroline Ummenhofer is at the forefront of developing a dynamic understanding of how the ocean affects the climate system. She has done particularly creative work in helping to understand the mechanisms of how ocean properties give rise to changes in large-scale atmospheric circulation that impact rainfall on land. Her core research discoveries have been in tropical climate variability, particularly in the Indian Ocean; the linkages between ocean variability and atmospheric blocking outside the tropics; and the connections between the Hadley Circulation and the ocean’s eastern boundaries. In each area, Caroline has made very substantial contributions. For example, prior to her highly cited 2009 paper in Geophysical Research Letters, it was thought that the most damaging droughts experienced in Australia were caused by Pacific Ocean conditions. However, she showed convincingly that conditions in the Indian Ocean were the real cause.

Caroline has worked with a variety of colleagues on a wide array of climate problems over millennial timescales to modern seasonal predictions. She introduces new techniques and concepts in her work and always has an eye toward the implications for society. She has taken a particular interest in showing the connections between ocean conditions and the extremes of drought and flood that influence crop yields. She has made exceptional contributions to understanding the ocean’s influence on rainfall in Australia, the United States, Southeast Asia, and Africa. She is a leading expert on the expansion of the tropics and drying of the subtropics predicted with global warming. She has taken on leadership roles in national and international projects like Climate and Ocean: Variability, Predictability and Change (CLIVAR) while maintaining a truly remarkable production rate of original scientific research. Her dynamical insights are deep, the problems she tackles are hard, and her approaches are novel and creative. She is a rising star in ocean and climate science and has already had a global impact.

On a personal level, I have to say that it has been a wonderful experience to have Caroline as a colleague for the past 6 years. I marvel at her productivity, her prodigious travel schedule, her skill at building collaborative teams, her teaching ability, and her generosity to students, colleagues, and the community at large. I am certain that you will be hearing her name in connection with important discoveries about the climate system for many years to come. Please join me in congratulating Caroline for her well-deserved honor of the James B. Macelwane Medal.

—Raymond W. Schmitt, Woods Hole Oceanographic Institution, Mass.

Thanks, Ray, for your kind words—and your relentless support and encouragement over the years. I also want to thank my nominators and the AGU Macelwane selection committee for their time and efforts. Science, and especially climate science, has become an intrinsically collaborative effort. The research leading to this medal was only possible through contributions from many colleagues around the world. I am continuously inspired by the wealth of groundbreaking research findings by the climate and geoscience community—many of whom are at least as deserving of this medal. The interdisciplinary nature of the field is what first drew me to ocean sciences and my degree in marine biology/oceanography at the School of Ocean Sciences, University of Wales, United Kingdom. Three individuals there in particular opened my eyes to the attraction of interdisciplinary research in biophysical interactions and paleoclimate that I enjoy at the Woods Hole Oceanographic Institution (WHOI) today, namely, Dave Bowers, David Thomas, and James Scourse. From north Wales to New South Wales, half way around the globe, an 8-week internship in Sydney, Australia, turned unexpectedly into the best 8-year Ph.D. and postdoc experience I could have wished for. I am deeply grateful to my adviser, Matthew England, for his unstinting support and generous mentorship ever since that email about hosting my internship—and for teaching me how to be a productive, creative, and collaborative scientist. I also found a wonderful team of close colleagues-turned-friends at the University of New South Wales, particularly with Alex Sen Gupta and Andrea Taschetto. My research on Australian rainfall and Indian Ocean dynamics was greatly enriched by interactions with colleagues at CSIRO (Peter McIntosh, Gary Meyers, Mike Pook, James Risbey). Long-standing collaborations with colleagues at the Lamont Doherty Earth Observatory (Rosanne D’Arrigo, Brendan Buckley), Claus Böning and Arne Biastoch (GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel), Jerry Meehl (National Center for Atmospheric Research), and Rhawn Denniston (Cornell College) also shaped my research. I’ve been fortunate over the years to be able to rely on wonderful administrative staff and would like to thank them for all their hard work that supports all our scientific endeavors. At WHOI, I found a stimulating collaborative environment ideal for exciting new interdisciplinary research, made so by the individuals working there. Too numerous to all name here, I am indebted to Ray Schmitt as my key mentor and also thank my close collaborators Young-Oh Kwon and Hyodae Seo, as well as a dynamic group of postdocs and students. It feels like I receive this award as a representative of a larger collective—and I constantly cherish the opportunities to work with many inspiring researchers from different disciplines to tackle key questions in the field of climate science and its societal applications. —Caroline C. Ummenhofer, Woods Hole Oceanographic Institution, Mass.