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Nitrous oxide fluxes in the central and eastern South Pacific
Author(s) -
Charpentier José,
Farías Laura,
Pizarro Oscar
Publication year - 2010
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 - 10.1029/2008gb003388
Subject(s) - pycnocline , upwelling , ocean gyre , oceanography , transect , halocline , subtropics , mixed layer , anticyclone , boundary current , geology , environmental science , atmospheric sciences , ocean current , ecology , salinity , biology
N 2 O air‐sea fluxes were continuously measured on a transect crossing the Subtropical South Pacific Gyre (SPG) from its central part toward its coastal boundary (associated with coastal upwelling off central Chile) during the BIOSOPE cruise (austral spring, 2004). Continuous N 2 O air‐sea fluxes in the central part of the SPG (132° to 114°W) were slightly negative (−0.48 ± 0.44 μ mol m −2 day −1 ), whereas in its eastern part (114°W to 81°W), they were slightly positive (0.41 ± 0.34 μ mol m −2 day −1 ), reaching up to 18 μ mol m −2 day −1 in the coastal area (130 km from the coast). The transition between oceanic and coastal conditions was characterized by an abrupt increase in N 2 O emissions from 80°W eastward and was associated with an increase of surface Chl‐a contents. This trend corresponded to the change in trophic status from very oligotrophic to eutrophic. The outward (through the air‐sea interface) and inward (through the pycnocline) N 2 O fluxes of the surface layer (SL) were also determined at three representative stations, taking into account turbulent diffusion and vertical advection. The N 2 O released into the atmosphere from the eastern part of the SPG came largely (70–80%) from the N 2 O produced in the SL (2.0 × 10 −3 μ mol m −3 day −1 ). In the coastal area, N 2 O production in the SL reached up to 1.16 μ mol m −3 day −1 , and 28% of the N 2 O released into the atmosphere was upwelled though the pycnocline by Ekman transport. The annual N 2 O emissions estimated for the eastern South Pacific reach 50 Gg of N 2 O, confirming the importance of this region for global emissions and reaffirming coastal upwelling centers as areas of strong production and outgassing.