Isaac R. Santos

Southern Cross University

2018 James B. Macelwane Medal Winner

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.”


Isaac Santos is not only an outstanding Earth scientist but also a brilliant science communicator and student mentor. With training in chemical oceanography at Florida State University under Bill Burnett, Isaac recognizes the interdisciplinary nature of our field and works collaboratively at the edge of conventional disciplinary boundaries.

Isaac uses geochemical tracers to resolve the drivers and biogeochemical implications of submarine groundwater discharge (SGD). He made elegant demonstrations that SGD is a major source of greenhouse gases and carbon to the coastal ocean and developed substantial arguments for the importance of SGD at a variety of coastal sites, including mangroves, coral reefs, estuaries, and beaches. Isaac’s innovative research relies on his vision of taking the lab to the field. He combined automated observations of radioactive and stable isotope tracers to obtain real-time and high-precision data in situ. These techniques allowed Isaac to collect unique data sets to address complicated and important interdisciplinary questions in hydrology, biogeochemistry, and oceanography. His diverse research has inspired colleagues and government agencies to consider the implications of SGD to coastal biogeochemical cycles and water quality.

Isaac’s dedication to science goes beyond the quest for new knowledge. Isaac should also be recognized for his broader contribution to our community and gregarious approach to work and student supervision. He is an unselfish colleague leading a large and productive research group. He always shares his best ideas and projects with his students. His leadership, combined with his great ability in developing collaboration and building first-class infrastructure, will help to ensure long-lasting impacts of his work. Isaac is a candid and idealistic advocate on issues of public interest. By engaging with the public and the mainstream media, his research has influenced public opinion and is helping to manage and preserve valuable coastal waterways while encouraging the fossil fuel industry to prevent greenhouse gas leakages from aging infrastructure.

With balance in research, teaching, and outreach as well as life outside academia being a desire of all, Isaac has achieved just that. Achieving balance extends his positive influence to our future generation of scientists. His outstanding track record of discovery, focus on student development, collaborative mindset, and engagement with the broader society are fully in line with AGU’s values and mission. His many and important contributions published in >100 papers, commitment to the well-being of his students, and spirit of generosity make him a well-deserved winner of the James B. Macelwane Medal.

—Ling Li, Westlake University, Hangzhou, China


Winning an AGU medal makes me feel nostalgic and grateful. It brings memories from where I come from and all the people who supported me along the way. It enlightens a path to the future.

As an undergrad in Rio Grande (Brazil), I would read AGU journals as I learned English. I would dream about publishing there. I didn’t dream about winning a medal. As a Brazilian working in regional Australia, being singled out with a medal takes me a step closer to overcoming a self-diagnosed impostor syndrome.

I am thankful for Ling’s generous nomination and honored to have worked with him. He mentions the achievement of work-life balance, but I am afraid my wife, Ana, may occasionally disagree with this. On these occasions, I often apologize and remind her that a 20-year marriage requires true love. Instead of balance, I have blended work and life as I care for my young family and students at the same time. I would achieve nothing without family encouragement and understanding.

Investigating submarine groundwater discharge requires truly interdisciplinary approaches and collaboration. My lifelong mentors Bill Burnett, Jeff Chanton, Thorsten Dittmar, Felipe Niencheski, and Emmanoel Silva-Filho have been role models inspiring me along the way. Thanks to my friends and collaborators Guilherme Lima, Rick Peterson, Christian Sanders, Damien Maher, Doug Tait, and many others whom I cannot mention in 400 words.

It is an exciting time to work on submarine groundwater discharge! I often say that submarine groundwater discharge has been put on the “to-do list” or in the “too hard basket” for long enough. Our new tools are revealing leaky shorelines worldwide, helping us to quantify the invisible, and demonstrating major implications to marine biogeochemistry. We are learning how the underground routes of biogeochemical cycles provide climatic feedbacks as groundwater releases soil carbon and nutrients to the oceans.

Macelwane was deeply interested in education. He saw himself as a servant to students, and I am proud to be associated with his vision. As researchers, we often strive for independence and can easily become too self-centered. Students unconsciously remind me of what research is all about. Their seemingly simple but penetrating questions, fresh perspectives, and full commitment to improving our world give real meaning to my research. Thanks to current and past students for raising the bar every day, keeping me grounded, and pushing me outside comfort zones—I owe this medal to you!

—Isaac Santos, Southern Cross University, Lismore, Australia