NSF Postdoctoral Fellow – Stanford Environmental Earth System Science
Category Archives: H2 Fluxes @ Harvard Forest
I measure the flux of H2, both above and below the temperate forest canopy at Harvard Forest in central Massachusetts, with the goal of contributing to our understanding of the significant microbial soil sink for atmospheric hydrogen.
A manuscript I’ve been working on for a good chunk of time now, entitled “Ecosystem fluxes of hydrogen: a comparison of flux-gradient methods,” was just published to Atmospheric Measurement Techniques Discussions (view paper online). Our goal was to present a detailed experimental approach for measuring ecosystem fluxes of H2 and to test different so-called “flux-gradient methods” for calculating the H2 fluxes. Some common trace gas flux methods, e.g. eddy covariance, are not available for species like H2 that cannot be measured precisely at high frequencies (<1Hz). We hope this paper will help inform the design of future studies for which flux-gradient methods might be the best option for measuring trace gas fluxes.
I was thrilled to give a talk this year at AGU in the full-day, highly subscribed Biosphere-Atmosphere Greenhouse Gas Fluxes in Terrestrial Ecosystems IV session organized by Paul Stoy, Christopher Williams, and Todd Scanlon. I’m looking forward to publishing these results very soon!
I defended my thesis entitled “Field Measurement of the Fate of Atmospheric H2 in a Forest Environment: from Canopy to Soil” on October 4, 2012.
It was an incredible relief to finish the thesis document itself (link to .pdf; Carl-Gustaf Rossby Prize for best PhD thesis in PAOC for the year). I really enjoyed preparing and giving my thesis defense presentation. It’s not often that one gets to present the culmination of six years of hard work and personal development to colleagues, family, and friends. I am grateful for mentorship from my advisor Ron Prinn, my thesis committee (Steve Wofsy – Harvard, Bill Munger – Harvard, Tanja Bosak – MIT, Colleen Hansel – WHOI, Shuhei Ono – MIT), and many others along the way!
I am continuing at MIT for a short (approximately 9 month) postdoctoral position with Ron Prinn to translate the work described in my thesis to publications. I am currently exploring possibilities for a postdoctoral position at the intersection of microbial ecology and atmospheric chemistry (trace gas cycles or aerosols) by searching advertised positions and writing fellowship proposals.
Micro-organisms have produced dramatic shifts in the composition of the Earth’s atmosphere and continue to be important drivers of ocean- and land-atmosphere exchanges of gases that have a strong influence on atmospheric composition and climate. An interesting example is the microbial influence on atmospheric molecular hydrogen (H2), which dominates the fate of this gas in the atmosphere. H2 is emitted to the atmosphere by about half natural and half anthropogenic, or human-induced, processes but it is predominantly removed from the atmosphere by microorganisms in the soil, which makes this process the most important, yet least understood, player in the atmospheric H2 budget.
I just returned to Boston after the six weeks of travelling. My two weeks in California, filled with conferences and colleagues, was quite different from the intensive and somewhat isolated period spent in India.
Presenting my poster at AGU - one of 12,000+ posters
First stop was San Diego, where I attended the 44th Meeting of Advanced Global Atmospheric Gases Experiment (AGAGE) Scientists and Cooperating Networks at the Scripps Institute of Oceanography in La Jolla. Anita Ganesan’s instrument in Darjeeling may pave the way for the first AGAGE site in India, so the crowd was eager to hear her describe our success in deploying her instrument. Her dedicated and diligent work is paying off as she is collecting some of the first high precision direct greenhouse gas measurements in India.
I gave a talk at the AGAGE meeting on my recent work on the flux of H2, CO2 and COS between the soil and atmosphere at Harvard Forest. I focus on the persistence of soil-atmosphere exchange of trace gases across snowpack, which insulates the soil microbial community from freezing air temperatures while allowing trace gases to diffuse through the porous snow matrix. I’m interested in how strongly the biogeochemical cycling continues throughout the winter and in comparing the behavior of the different cycles in the low temperature ‘incubator’ beneath the snow. Continue reading →
Instrument installation is finally complete and things have been running smoothly through the fall and winter seasons. Here are some photos of the installation and current setup, and of the forest in general.
The porcupine was first spotted in the fall during a lunch break at the Harvard Forest Environmental Measurement Site instrument shed. It continued to reside beneath the shed as was clearly evident by the snow tracks (or more like a trough) leading to a nearby chewed on balsam fir. I set up a crittercam to record the action, and have compiled a “best of” video of our porcupine waltzing through the snow…
Two years after embarking on my thesis project to design and build a custom instrument that measures hydrogen fluxes, I deploy my creation to the Harvard Forest Long Term Ecological Research site in Petersham, Massachusetts. The instrument shed is tight, but with the help of colleagues at Harvard University, the move is successful. In this short documentary by co-student Ryan Abernathey we introduce the forest and the project, but the work has only just begun…