Manuscript presenting first yearlong study of carbonyl sulfide fluxes

Harvard Forest EMS tower
Harvard Forest EMS tower

Our manuscript on the “Seasonal fluxes of carbonyl sulfide in a midlatitude forest” was just recently published in PNAS (document online). Lead author Róisín Commane and I met at Harvard Forest where she installed an Aerodyne Research Inc., laser spectrometer to study the seasonal behavior of carbonyl sulfide (interchangeably called OCS and COS by different groups). Of particular interest are the common pathways to both CO2 and OCS, for example both trace gases react with carbonic anhydrase enzymes in leaves. This commonality may provide a quantitative, independent measure of the photosynthetic pathway for carbon assimilation.

In this study, we find that vegetative uptake accounted for 72% of annual uptake of OCS, and nighttime uptake through stomata and soil uptake accounted for the remainder. Emissions of OCS from the forest canopy and soils were observed episodically at the forest, and by an unknown mechanism.

We find that OCS and CO2 are in certain cases affected by different processes, making their relationship variable. Thus, OCS cannot be used as a direct tracer of photosynthetic activity, but can probe various aspects of ecosystem activity, such as stomatal conductance, which will be useful for constraining aspects of carbon cycling models.

Is H2 an upper atmospheric tracer?

I presented a poster at the 2010 American Geophysical Union General Assembly on H2 as a “mesotracer.” A rare glimpse into the chemical and dynamical evolution of the Arctic polar vortex is provided by a suite of in situ balloonborne measurements. A set of mesospheric tracers observed in the late vortex validate theoretical mesospheric chemical profiles, which is especially valuable for the case of mesospheric H2. Early vortex mesospheric profiles are constructed to explain mixing in tracer-tracer space. Expanding a model to incorporate three mesotracers, H2, CO, and SF6, instead of only one, will increase our ability to constrain estimates of the amount of mesospheric air that descended to stratospheric altitudes by vortex end.

AGU 2010 - Chemical tracers in the upper atmosphere
AGU 2010 Poster – Chemical tracers in the upper atmosphere