2021 Arthur L. Day Medal

Presented to Katherine Freeman

Katherine Freeman

Katherine Freeman
Pennsylvania State University


Citation by Ariel Anbar and Claudia Mora

Professor Katherine Freeman’s name is synonymous with the field of compound specific stable isotope analysis. As a graduate student at Indiana University, Freeman was part of the first team to accomplish these measurements. Subsequently, her pioneering research utilized this innovation to develop isotope proxies for paleoenvironmental parameters such as partial pressures of atmospheric CO2 and precipitation. Her research into the relationship between algal lipid carbon isotopic fractionation and concentrations of dissolved CO2 established the basis for a pCO2 proxy, leading to critical insights into the coupling of atmospheric CO2 with global temperature and climate during the Paleogene. She used carbon isotopes to examine the emergence and expansion of C4 plants in past terrestrial ecosystems, and laid the foundation for using leaf wax hydrogen isotope compositions to characterize soil waters and precipitation. Her recent collaborative efforts address the intimate connections between water availability, plant physiology, and early human habitation in eastern Africa. Exemplifying the highest aspirations of our field, Professor Freeman is exceptionally deserving of the Arthur L. Day Medal.


Response by Katherine Freeman

My sincere thanks to my amazing colleagues, Claudia Mora and Ariel Anbar for their kind words and efforts on my behalf. I am delighted and deeply honored to receive the Arthur L. Day Medal today and I am humbled to stand in the company of its prior recipients. I am grateful to the GSA and especially to those who made it possible to celebrate all the awardees, including those from last year, in person.

I enjoyed unbelievably good fortune in mentors, including Tom Hoering, Stuart Wakeham, and, especially John Hayes. John was my doctoral advisor at Indiana University, and it was his vision for compound-specific isotope analyses that opened a rich and exciting scientific frontier that I have been exploring ever since. I miss him, but his unlimited enthusiasm for isotopes, biogeochemistry, and mass spectrometry continue to inspire me.

This honor is a tribute to the students and postdocs that made my research possible. It has been a privilege--and great fun--to work alongside and learn from each one of them. This month marks my 30th year on the faculty at Penn State, a fact that I find startling. I am grateful to work in a place that has allowed me to flourish, with fabulous colleagues and a supportive administration.

I dedicate this to my late father. He gave me my first chemistry set when I was a young girl, and then supported my aspirations and celebrated my successes for the next five decades. I also thank my own children: Sam and Leah, who make me proud in countless ways, but especially because they are kind and generous humans. And most of all, my heartfelt thanks to Mark, who puts up with my ridiculousness and enriches my life with his love.