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Grad student talk - Northern hemisphere ethane and propane trends and CFC flux through snowpack

Thursday, February 18, 2016, 12:00PM - 1:00PM


Sam Rossabi


SEEC room S225

In this seminar, I will discuss work on Northern Hemisphere atmospheric trends of ethane and propane, and proposed future work on chlorofluorocarbon (CFC) flux through snowpack.

Ethane and Propane Trends: Ethane and propane are important precursors to tropospheric ozone and aerosol formation. Studies of firn air from Summit, Greenland have shown concentrations of these gases have been declining for 40 years, however, recent analysis of data from a global monitoring network suggests this trend reversed in the late 2000s. Trends are most significant in the central and eastern United States and downwind of this region. The largest source of ethane and propane is fossil fuel production and use. Combined with the apparent source region, this suggests increased ethane and propane emissions are a result of increased oil and natural gas production.

Proposed Future Work: A pilot study conducted in March 2009 found evidence of a terrestrial sink of CFC through snowpack at Niwot Ridge. CFC are responsible for stratospheric ozone destruction, and were previously thought to be destroyed exclusively in the upper atmosphere. The 2009 study suggests that under snow biogeochemical activity consumes CFC. The proposed study will take place over entire winter seasons at Niwot Ridge and Toolik Lake, Alaska. A multi-inlet sampling manifold will allow for air sampling within the snowpack and for calculation of gas fluxes between inlets. These experiments will allow for estimation of the terrestrial sink of these compounds. If the sink is found to be of the same order of magnitude of chemical loss processes, it will be incorporated in atmospheric models to improve representations of CFC lifetimes, and to more accurately estimate the recovery rate of stratospheric ozone.