4. Greenhouse gas fluxes from the land/sea margin and the coastal zone
The land/sea margin, intertidal zone, and coastal waters are critically under-examined in terms of their contribution to greenhouse gas fluxes and their contribution to climate change feedbacks. This is particularly noteworthy because the human race is in the midst of an unintended experiment in coastal environments, in which large amounts of anthropogenic nutrients are being conveyed to coastal environments by rivers, atmospheric inputs, and groundwater. As a result, biological productivity and rates of many biogeochemical processes in coastal zones are increasing. Well-documented consequences of this widespread nutrient enrichment include depletion of oxygen and decrease in oxidation/reduction potential in bottom waters and sediments. High-profile examples include Long Island Sound, Chesapeake Bay, and the Gulf of Mexico. An important consequence of the anoxic diagenesis of organic matter in marine sediments is production of nitrous oxide (N2O) and methane (CH4), significant anthropogenic greenhouse gases. The climate forcing of CH4 and N2O is enhanced by ~25 times (CH4) to 320 times (N2O) on a molecule-for-molecule basis relative to CO2. Because of this, CH4 and N2O collectively contribute roughly a quarter of the current anthropogenic radiative forcing (IPCC Summary for Policy Makers, February, 2007).
Despite the well-known high productivity and anthropogenic changes occurring in coastal environments, greenhouse gas fluxes from these regions are poorly known, are probably underestimated, and are largely ignored in global budgets (Bange, 2006a, b). Furthermore, the roles of land/sea coupling and the coastal zone in U.S. and global carbon budgets are not well understood (Ocean Carbon and Climate Change Program, Doney and others 2004). It is likely that the coastal zone in general, and both intertidal and anoxic sediments in particular, are important locations for flux to the atmosphere of the greenhouse gases N2O, CH4, and CO2 at rates that are significant to national and global budgets. In addition, feedbacks may exist such that continuing nitrogen enrichment of coastal landscapes, and continuing climate change and sea level rise, will cause the rates of greenhouse gas production in the coastal zone to increase in coming years.
This research opportunity is broadly concerned with the role of coastal ecosystems as both source and sink for the greenhouse gases CO2, N2O, and CH4. The specific focus within that proposed area of research will be determined by the interests and background of the successful candidate. The approach is anticipated to be largely experimental, although modeling could be an important component of the research. Some potential research topics include, but are not limited to, examination of:
Instrumentation relevant to this project that is available at the USGS Woods Hole Science Center includes gas chromatographs with electron-capture and flame-ionization detectors, a LI-COR CO2 analyzer, field deployable nitrous oxide, NOx and other related sensors, a CHN analyzer, RAD7 radon analyzers, RaDeCC instrumentation for measuring short-lived radium isotopes, and a gamma counter. Instrumentation is also available at the adjacent Woods Hole Oceanographic Institution, at the Marine Biological Laboratory, and in the labs of other academic and USGS colleagues for a variety of stable isotope and radioisotope analyses, noble and other gas analyses, ICPMS, and nutrient analyses. Proposals involving new collaborations to expand analytical or other capabilities are welcome. This research will benefit from extensive marine operations infrastructure at the USGS Woods Hole Science Center and from significant synergy with our ongoing examinations of biogeochemistry, hydrology, and gas exchanges in watersheds, at the land/sea margin, and in the coastal ocean (e.g. Sundquist 1993; Sarmiento and Sundquist, 1992; Sundquist and Visser, 2003; Crusius and Wanninkhof, 2003; Crusius and others, 2005, in review; Bratton and others, 2004, 2007; Kroeger and others, 2006, 2007, in review).
REFERENCES
Bange, H.W., 2006a, Estuarine Coastal And Shelf Science. 70: 361-374.
Bange, H.W., 2006b, Atmospheric Environment. 40: 198-199.
Bratton, J.F., Böhlke, J.K, Manheim, F.M., and Krantz, D.E., 2004, Ground water beneath coastal bays of the Delmarva Peninsula: Ages and nutrients. Ground Water 42: 1021-1034 .
Bratton, J.F., Böhlke, J.K., Krantz, David E., and Tobias, C.R., accepted for publication, Flow of groundwater beneath a back-barrier lagoon: Geometry and geochemistry of the subterranean estuary at Chincoteague Bay, Maryland. Marine Chemistry.
Crusius, J., and R. H. Wanninkhof, 2003, Gas transfer velocities measured at low wind speed over a lake, Limnology and Oceanography 48:1010-1017.
Crusius J., Koopmans D., Bratton J.F., Charette M.A., Kroeger K.D., Henderson P., Ryckman L., Halloran K., and Colman J.A, 2005, Submarine groundwater discharge to a small estuary estimated from radon and salinity measurements and a box model. Biogeosciences 2:41-157.
Crusius, J., Berg, P., Koopmans, D.J. and Erban, L, in review, Eddy correlation measurements of groundwater discharge. Marine Chemistry.
Intergovernmental Panel of Climate Change, 2007, Climate Change 2007: The Physical Science Basis, Summary for Policy Makers, February 2007.
Kroeger, K.D., Cole, M.L., and Valiela, I., 2006, Groundwater-transported dissolved organic nitrogen exports from coastal watersheds. Limnology and Oceanography 51: 2248-2261.
Kroeger, K.D., Swarzenski, P.W., Greenwood, J., and Reich, C., 2007, Submarine groundwater discharge to Tampa Bay: Nutrient fluxes and biogeochemistry of the coastal aquifer. Marine Chemistry 104:85-97.
Kroeger, K.D. and Charette, M.A, in review, Submarine groundwater discharge: Nitrogen biogeochemistry of the discharge zone. Limnology and Oceanography.
Ocean Carbon and Climate Change Program, 2004, Ocean Carbon and Climate Change: An Implementation Strategy for U.S. Ocean Carbon Research, S.C. Doney (ed.).,109 pp.
Sundquist, E.T., 1993, The global carbon dioxide budget. Science 259:934-941.
Sarmiento, J.L., and Sundquist, E.T., 1992, Revised budget for the oceanic uptake of anthropogenic carbon-dioxide. Nature 356. 589-593.
Sundquist, E.T., and Visser, K., 2003, The geologic history of the carbon cycle. In: Treatise on Geochemistry (vol. 8: Geochemistry) (eds. H.D. Holland and K.K. Turekian), Elsevier: New York.
Proposed Duty Station: Woods Hole, MA
Areas of Ph.D.: Chemistry, biogeochemistry, oceanography, geology, hydrogeology, soil Science, environmental science, microbiology, or other appropriate field
Qualifications: Applicants must meet one of the following qualifications: Research Chemist, Research Oceanographer, Research Hydrologist, Research Geologist
(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.)
Research Advisor(s): Kevin Kroeger, (508) 457-2270, kkroeger@usgs.gov; John Crusius, (508) 457-2353, jcrusius@usgs.gov; Eric Sundquist, (508) 457-2397, esundqui@usgs.gov; John Bratton, (508) 457-2254, jbratton@usgs.gov
Human Resources Office contact: Kathy McDuffie, (703) 648-7408, kmcduffie@usgs.gov
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Summary of Opportunities |