Understanding Recent Changes in the Atmospheric Methane Growth Rate through Analyses of the Isotopic Composition of Methane in a Rare Air Archive

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The primary objective of this project is to better understand recent trends in the growth rate of atmospheric methane (CH4) through: (1) analysis of the isotopic composition of CH4 over two decades using samples from the Oregon Graduate Institute (OGI) air archive and (2) the interpretation of long-term and interannual variations in atmospheric CH4 in terms of changing CH4 sources and sinks. More than 380 samples originally collected at Cape Meares, Oregon (1978-1998), Palmer Station, Antarctica (1991-1997), and Point Barrow, Alaska (1995-1998) will be analyzed for their CH4 isotopic composition (13C/12C and D/H). The resulting dataset will provide the only northern hemisphere time series record of 13C/12C available prior to 1988, and the only one at monthly resolution in any case. Equally important, the D/H time series will be the only record available prior to 1996. Results will be merged with more modern records creating a 30 year composite record and interpret the results of the changing concentration and isotopic composition of CH4 in terms of changing biogenic, fossil, and pyrogenic sources of CH4 over this time period.The hands-on research opportunities for Portland State University undergraduate and graduate students provided through this project in an area of cutting edge research will enhance their development and build a foundation for the next generation of Earth science research. Building a partnership with the Portland Apprenticeships in Science and Engineering Program will initiate and foster a relationship of mentoring with local high school students during summers and provide the framework for conveying the excitement and challenges of science exploration to promising young students before they commit to fields of focus in college.