Aquatic Sciences Meeting, Albuquerque 2001

PC18 Biogeochemical Cycles

Date: Thursday, February 15, 2001

Location: Southwest Hall

Westley, M, B, University of Hawaii, Honolulu, USA, mwestley@soest.hawaii.edu

Popp, B, N, University of Hawaii, Honolulu, USA,

Rust, T, M, University of Hawaii, Honolulu, USA, trust@soest.hawaii.edu

Sansone, F, J, University of Hawaii, Honolulu, USA, sansone@soest.hawaii.edu

A SHALLOW SOURCE OF NITROUS OXIDE IN THE EASTERN TROPICAL NORTH PACIFIC.

Although the oceans are known to be a major natural source of the potent greenhouse gas nitrous oxide, the magnitude and characteristics of this source are poorly constrained. Recent work in the subtropical North Pacific using the stable isotopic compositions of nitrous oxide identified subsurface production, probably by bacterial nitrification, as a significant source of nitrous oxide to the atmosphere. This discovery motivated the May-June 2000 Eastern Pacific Redox Experiment (EPREX), a west-to-east transect from the oligotrophic, oxygen-rich waters of the subtropical North Pacific near Hawaii (22.75N, 158W) to the highly-productive, oxygen-poor waters of the eastern tropical North Pacific near Mexico (15N, 98W). We collected water samples at depths ranging from 2000 meters to the surface at six stations along the transect to establish concentration profiles of oxygen, ammonium, nitrite, nitrate and nitrous oxide and dual stable isotope profiles of nitrous oxide. We will present these profiles, identify mechanisms of nitrous oxide production under different biogeochemical regimes, and evaluate the significance of a shallow oceanic source to the global tropospheric budget of nitrous oxide.

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Aquatic Sciences Meeting, Albuquerque 2001

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