Citation

Response

Jianghui Du received the 2019 Harry Elderfield Student Paper Award at AGU’s Fall Meeting 2019, held 9–13 December in San Francisco, Calif. The award “recognizes an exemplary manuscript by a graduate student working toward their Ph.D.”

Citation

Jianghui Du is a most deserving recipient of the Harry Elderfield Award of the AGU Paleoceanography and Paleoclimatology section. Du’s Ph.D. work at the College of Earth, Ocean, and Atmospheric Sciences at Oregon State University exemplifies Harry Elderfield’s style, rooted in impeccable laboratory analytical skill, in creative application of geochemistry to important outstanding paleoceanographic problems, and in thinking anew about fundamental processes to overturn standard interpretations. Beyond his individual scholarship, Du is noted for peer mentoring of other students, again reminiscent of Elderfield’s generous collaborative style. The paper honored here by Du et al., “Flushing of the deep Pacific Ocean and the deglacial rise of atmospheric CO2 concentrations” (Nature Geoscience, 2018), opens a new window into understanding past changes in the abyssal Pacific circulation recorded by authigenic neodymium isotopes in deep-sea sediments. Du shows that for this tracer, where water residence times are relatively short, as in the deep Atlantic, conservative mixing dominates. But where water residence times are longer, such as in the deep Pacific, nonconservation driven mostly from chemical interactions with the seafloor dominates. By including both terms in quantitative models, Du explains perplexing data, resolves conflicts in geochemical budgets, and infers large variations in the deep Pacific circulation rate during the transition from glacial to interglacial conditions. His work further reveals a potential mechanism for flushing carbon from the deep Pacific to the atmosphere at the end of the last ice age. New thinking raises new questions, and these fresh insights will motivate further work. Du’s willingness to buck convention and think anew about difficult problems is worthy of celebration. We expect to hear much more from Jianghui Du as he moves beyond graduate school to a postdoctoral position at ETH Zürich, and we congratulate him on this richly deserved award.

—Alan C. Mix and Brian A. Haley, Oregon State University, Corvallis

Response

I thank Alan and Brian for their generous citation comments and the AGU Paleoceanography and Paleoclimatology Award Committee for selecting my work for the 2019 Harry Elderfield Outstanding Student Paper Award. I feel particularly honored to receive an award named after one of the founders of my chosen field, rare earth element ocean chemistry and paleoceanography. The complex interactions between the ocean, the solid Earth, and the atmosphere, and the imprint of climate change on these interactions, turn a fascinating chemical problem into one that is both practical and important. I had the good fortune of building on some beautiful paleoceanographic records from recent field programs in the northeastern Pacific Ocean during my Ph.D. I am excited to start a career in paleoceanography at a time of rapidly expanding knowledge in the biogeochemical cycles of trace elements and isotopes in the modern ocean and of development of novel analytical tools that open new avenues of research. As a student, I experienced the full trajectory in the “Elderfield proxy confidence curve” of optimism, pessimism, and realism. I am particularly grateful to the National Science Foundation and other funding agencies for supporting this work, and to a group of mentors and peers at Oregon State and elsewhere whose steady support got me through the inevitable rough patches to the point of insight. I can only hope to follow in Harry Elderfield’s footsteps as an innovator and mentor, bridging the expanding fields of process-based knowledge of geochemical systems and paleoceanographic applications that help us to understand and thrive in a changing world.

—Jianghui Du, ETH Zürich, Zürich, Switzerland

Kassandra Costa will receive the 2018 Harry Elderfield Student Paper Award at AGU’s Fall Meeting 2018, to be held 10–14 December in Washington, D. C. The award recognizes “an exemplary manuscript from a Ph.D. graduate student and exceptional promise for continued contributions in the fields of paleoceanography and/or paleoclimatology.”

Citation

Kassandra Costa is a richly deserving recipient of the inaugural Harry Elderfield Award.

She is a remarkable junior scientist who already has multiple outstanding achievements to go along with her exceptional continued potential. During the course of 5 years in the Ph.D. program at Lamont-Doherty Earth Observatory of Columbia University, she combined sedimentology and geochemistry in innovative ways to provide insights into changes in the biological productivity, deep chemistry, and surface hydrography of the tropical and subpolar North Pacific Ocean during previous ice ages. Any one of her five thesis chapters might merit serious consideration for an award based on an exemplary student publication, including a paper on deep ocean redox changes that she published in the special volume of Geochimica et Cosmochimica Acta devoted to the memory of Harry Elderfield. Instead, the award was given by the Paleoceanography and Paleoclimatology section of AGU for Kassandra’s study of dust deposition, nutrient utilization, and biological productivity in the central equatorial Pacific Ocean during the last glacial period. In this paper, published in Nature, she combined precise analyses of nitrogen isotopes in microfossil foraminifera and uranium and thorium isotopes in bulk marine sediments, from a north–south transect of cores, to show that despite enhanced glacial dust deposition, there was no iron fertilization in that important part of the glacial ocean. She further pointed out the potential oceanographic connection to high latitudes in the Southern Hemisphere, where glacial iron fertilization may have stimulated productivity while at the same time diverting nutrients that would otherwise have been delivered via subsurface waters to the tropical ocean. This important study is only one example of Kassandra’s combination of intellectual curiosity and creativity, analytical versatility and excellence, and scientific insight and productivity. We are fortunate to have Kassandra Costa among us, and she is an excellent choice for the Harry Elderfield Award in 2018.

—Jerry McManus, Lamont-Doherty Earth Observatory, Palisades, N.Y.

Response

Thank you, Jerry, for your kind words, and thank you to the AGU Paleoceanography and Paleoclimatology Award Committee for selecting me for the honor of the 2018 Harry Elderfield Award. Like Harry Elderfield, I am fascinated by the transport and fate of elements in the environment and what they can tell us about the biological, chemical, and physical mechanisms that link the ocean, climate, and solid Earth systems today and in the past. With the encouragement and support of my innumerable mentors throughout graduate school, I have had the good fortune to explore many different facets of paleoceanography in the North Pacific. I can only hope to live up to Harry Elderfield’s exemplar, and his wide-ranging accomplishments in ocean chemistry, hydrothermal activity, and paleoceanography are an inspiration for what a full academic career may hold.

—Kassandra Costa, Woods Hole Oceanographic Institution, Falmouth, Mass.