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Nitrogen and oxygen isotopomeric constraints on the origins and sea‐to‐air flux of N 2 O in the oligotrophic subtropical North Pacific gyre
Author(s) -
Popp Brian N.,
Westley Marian B.,
Toyoda Sakae,
Miwa Tatsuya,
Dore John E.,
Yoshida Naohiro,
Rust Terri M.,
Sansone Francis J.,
Russ Mary E.,
Ostrom Nathaniel E.,
Ostrom Peggy H.
Publication year - 2002
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2001gb001806
Subject(s) - flux (metallurgy) , ocean gyre , stable isotope ratio , oceanography , atmosphere (unit) , seawater , new production , nitrogen , thermocline , atmospheric sciences , chemistry , geology , subtropics , nutrient , phytoplankton , meteorology , ecology , physics , biology , organic chemistry , quantum mechanics
Although the oceans are a significant source of the greenhouse gas nitrous oxide (N 2 O) to the atmosphere, the magnitude and characteristics of this source are poorly constrained. We present here stable isotope and isotopomer (intramolecular distribution of 15 N within the linear NNO molecule) results for N 2 O and oxygen stable isotopic data for dissolved O 2 from Station ALOHA in the subtropical North Pacific gyre near Hawaii. The results indicate shallow (∼100–300 m) in situ N 2 O production. Results of isotope mass balance models constrain the rate of N 2 O production and the sea‐to‐air flux of N 2 O. Results of an isotope mass balance model that takes into account the ratios of the vertical gradients in the isotopic abundances of N, O, N α (central N) and N β (terminal N) of N 2 O and the measured gradients of N 2 O concentration through the thermocline indicate that shallow in situ production contributed 40% to 75% of the sea‐to‐air flux of N 2 O. This model also indicates that the net sea‐to‐air flux of N 2 O was at least 0.4 μmol m −2 d −1 and could be as high as 1.0 μmole m −2 d −1 . These model results are not statistically different from the sea‐to‐air flux of N 2 O calculated using an empirical relationship between wind speed and gas transfer rate (1.1 ± 0.7 μmole m −2 d −1 ) derived from measured values for wind speed, temperature and the surface mixed layer concentration of N 2 O. These results can be used to better constrain the global N 2 O budget.