Dr. Laurence Yeung has been awarded a NSF Earth Sciences Postdoctoral Fellowship to develop a program of research and education at the University of California, Los Angeles. He will develop techniques to study the distribution of the exceedingly rare 18O2 isotopologue of O2 in the atmosphere, which can provide new constraints on glacial ice cover, terrestrial precipitation, and biosphere productivity over time. To accomplish this task, laboratory and modeling studies will be conducted to study the covariances between established isotopic tracers in O2 (i.e., 18O/16O and 17O/16O ratios) and the new 18O2 tracer during important processes: photosynthesis, respiration, and stratospheric photochemistry. Additional terrarium experiments will simulate the atmosphere-biosphere system at steady state. The current atmospheric O2 isotopologue budget will then be interpreted based on the results of these experiments, and the results will be validated against other measures of biosphere productivity and respiration in the modern era. This project lays the fundamental groundwork for understanding of how the atmosphere, hydrosphere, and biosphere co-evolved during past climatic changes; only with this type of understanding can the human imprint on the global biosphere be put into its proper historical context. In addition, the techniques to be developed will further have an impact on fields such as the atmospheric and ocean sciences to help them better constrain the distribution, mechanisms, and global importance of biological and abiological sources and sinks of oxygen.
Dr. Yeung will conduct in-class environmental science programs at local Los Angeles high schools,mentor undergraduate and graduate students, and give lectures at the International GeoBiology course for graduate students and postdoctoral scholars as part of his integrated educational program, which is aimed at a wide range of potential students.
We made the first precise measurements of 18O18O and 17O18O in the atmosphere (they are benign variants of the O2 we breathe). Surprisingly, their relative concentrations in the are determined not by the biosphere (as was originally hypothesized) but instead by a single gas-phase reaction. Field observations, experiments, and models were all developed and employed to support this discovery. Results have been published in a peer-reviewed journal and dissemenated at scientific conferences and seminars. More publications are in preparation as of this report's writing. The finding represents a fundamental broadening of our understanding of atmospheric O2. We have shown that atmospheric O2 records more about the Earth system than previously thought: Not only does O2 integrate changes in the biosphere and water cycle (it's the main reason we have any O2 at all), but it also contains information about atmospheric chemistry. The historic record of atmospheric O2 could therefore be used to understand how these components of the Earth system covary; because all of this information is contained within a single molecule, there should be little ambiguity in their chronological sequence. Additional applications of this tool, e.g., to study the movement of air between the stratosphere and the troposphere and to understand photosynthesis and respiration in the oceans, are underway. Two undergraduate women were mentored during this project. One is starting graduate studies in the fall, while the other is completing her undergraduate coursework. The PI also gave guest lectures at the 2011 International GeoBiology Short Course. Last, the project supported the development of PHDtv (www.phdcomics.com/tv), a social media-based outreach venture co-founded by the PI. PHDtv uses a combination of self-produced videos, animations, and a podcast to communicate the lives and loves of scholars in creative and compelling ways. Composed of graduate students, postdocs, and Jorge Cham of PHD Comics, the 5-member ‘start-up’ is committed to breaking down "science nerd" stereotypes in popular media while providing a fun environment in which to learn the latest scientific advances. As of this report's writing, the PHDtv YouTube channel has >13,000 subscribers and >1 million views.
