Arevalo-Martinez, Damian L.

Bange, Hermann W.

Brandt, Peter

Dengler, Marcus

Fischer, Tim

Kock, Annette

English

OceanRep

T. Fischer, A. Kock, D.L. Arévalo-Martínez, P. Brandt, M. Dengler, H.W. BangeNitrous Oxide Fluxesin the EasternTropical Atlantic Ocean BMBF-Verbundvorhaben   NordatlantikBMBF-Verbundvorhaben SOPRANRD 1   Ocean Circulation and Climate DynamicsDüsternbrooker Weg 20D-24105 Kielcontact: tfischer@geomar.de      www.geomar.de      N2O       10% to 40% is from the oceanFlux measurements in 3 locations of expectedly high oceanic N2O emissionsMauritanian upwelling            Guinea Dome Region                    Equatorial cold tongueN2O mixed layer budget discrepancy in coastal upwelling and open oceanReferences                                                                    Kock, A., J. Schafstall, M. Dengler, P. Brandt, and H. W. Bange (2012):  Sea-to-air and diapycnal nitrous oxide fluxes in the eastern                                                                    tropical North Atlantic Ocean, Biogeosciences, 9, 957-964 -----  Nevison, C.D., R.F. Weiss, and D.J. Erickson III (1995): Global ocea-nic emissions of nitrous oxide, J. Geophys. Res., 100, C8, 15809-15820 ---- Ravishankara, A.R., J.S. Daniel, and R.W. Portmann (2009): Nitrous Oxide (N2O): The Domi-nant  Ozone-Depleting Substance Emitted in the 21st Century, Science, 326, 123-125 ----- Schafstall, J., M. Dengler, P. Brandt, and H.W. Bange (2010): Tidal inducedmixing and diapycnal nutrient fluxes in the Mauritanian upwelling region, J. Geophys. Res., 115, C10014 ----- Suntharalingam, P., and J.L. Sarmiento (2000): Factorsgoverning the oceanic nitrous oxide distribution, Global Biogeochem. Cycles, 14, 429-454 ---- Tsai, W.T., and K.K. Liu (2003): An assessment on the effect of sea sur-face surfactant on global atmosphere-ocean CO2 flux, J. Geophys. Res., 108, 3127  -----  Weiss, R.F., F.A. VanWoy, and P.K. Salameh (1992): Surface water and atmos-pheric carbon dioxide and  nitrous oxide  observations by shipboard automated gas chromatography,  Scripps Inst. of Oceanogr. Reference 92-11, San Diego,  Ca.Acknowledgments                                                                                                                          This study was supported by German Federal Ministry of Education and Research through                                                                                                                          the co-operative projects SOPRAN and NORTH ATLANTIC. Large parts of data acquisition also profited from participation in 3 cruises to the Tropical Atlantic that were part of the German Science Foundation‘sSonderforschungsbereich 754 - „Climate Biogeochemistry Interactions in the Tropical Ocean“. We acknowledge the support of the European Commission(FP7 - EuroSITES grant agreement No. 202955). The assistance of numerous grad students in taking microstructure profiles, and the friendly support of allcrew members of research vessels METEOR, MARIA S. MERIAN and POSEIDON are highly appreciated.Effects of N2O emitted to the atmosphereN2O producers Where is N2O emitted from the ocean ?- In upwelling systems- In regions where oxygen  minimum zones occur in   the water columnN2O is currently the most impor-tant ozone depleting substance[Ravishankara et al. 2009].Image of molecule created by Ben Mills / Global Warming ArtA main suspect in coastal upwelling systems: surface slicks  30 oW   25 oW   20 oW   15 oW   10 oW    5oW    0o     5oE   10 oS    5oS    0o     5oN   10 oN   15 oN   2021222324252627282930−4−3−2−10SST° C 10nmolm2 s      3 0oW   2 0oW   1 0oW    0 o   1 0oE   1 0oS    0 o     1 0oN   3 0oW   2 0oW   1 0oW    0 o    1 0oE   3 0oW   2 0oW   1 0oW    0 o    1 0oE   May 15 Jun 15 Jul 156 8 10 12 14 16 18 20 22−40−20020406080N2O concentration nmol/kgdepth below mixed layer depthsurface diapycnalfluxsea-to-air fluxMLD Sea-to-air flux versusdiapycnal flux from belowN2O profiles fromdiscrete samplesMeasurements of diapycnal mixing allow estimates of diapycnal fluxDeveloping cold tongue in boreal summer of 2011Diapycnal N2O upward flux to MLLow N2O fluxesin the region of the Oxygen Minimum Zone (OMZ)High N2O fluxesin the coastal upwellingHigh N2O fluxesat the equator during cold tongue developmentSurface slicks cause smooth ‚oily‘ water without capillary wavesBlack patches and stripes in the satellite picture denote large regions void of capillary waves(Envisat SAR,   Peruvian upwel-ling)                 N2O sea-to-air fluxfrom underway and discrete samplesSST° C302025  40 oW   30 oW   20 oW   10 oW    0 o    10 oE   20 oE   10 oS    0 o    10 oN   20 oN   30 oN MauritanianUpwelling  Guinea Dome Region  EquatorialCold TongueSuntharalingam and Sarmiento [2000]with data from Weiss et al. [1992].Nevison et al. [1995]Surface N2O superstauration afterSuntharalingam and Sarmiento [2000]with data from Weiss et al. [1992].Strong mixing at the shelf breakKock et al. [2012]Schafstall et al. [2010]N2O O2N2O concentrations are related to O2. The deep oxygen minimum is isolated from the surface O2, and so is surface N2O isolated from deep OMZ N2O.???? ?? ???? ????? ????????????????? ???? ??? ??? ??????????? ???????????? ????? ?? ???? ??? ????? ????? ????????? ??? ????????????????????????? ??? ?????????? ??????? ??????????? ????? ??? ??????? ?????????? ??? ???????????????? ?? ???? ??? ??? ?????? ??????????????????????? ??????? ???????Parameterization of Tsai and Liu [2003] for surface slicks shows reduced gas exchange and remediates dicrepancies.  30 oW   25 oW   20 oW   15 oW   10 oW    5 oW    0 o     5 oE   10 oS    5 oS    0 o     5 oN   10 oN   15 oN Nitrifying microbes Denitrifying microbes                              Nirosococcus oceanus Watson ex Bergey‘s Manual of Systematic Bacteriology                              Tom E. MorrisN2O is accidentally released to the water by microbes, either as a bypro-duct during nitrifi-cation or as an intermediate pro-duct during deni-trification. direction of diapycnal N2O fluxcaused by diapycnal mixing.deep OMZIncreased diapycnal mixing at the shelf break is a major contri-butor to high N2O supply to the coastal mixed layer.N2O sea-to air fluxN2O sea-to-air flux and diapycnal supply from below are of the same magnitiude.Discrete sea-to-air fluxes are shifted 1 degree for convenience.    70 1)               10                  35       20 1)                 1                  50          2 1)               <1                            1 to 3    <1 to 5 1)Coastal Upwelling          Open ocean       Equatorial Cold TongueSea-to-air flux   Diapycnal flux   VerticaladvectionLateraladvectionN20 production in mixed layerIn the coastal upwelling and in the open ocean, the estimated total supply to the mixed layer cannot account for the estima-ted sea-to-air flux.For the equatorial data we cannot assume a closed budget: available data is from the onset of the cold tongue, in a phase of presumably rising N2O concentrations in the surface layer.Fluxes in   pmol/m2/s1)   Kock et al. [2010]O3 O2Kock et al. [2010]Picture courtesy ofW. AlpersJohannes Lampel           Reported N2O surface superstaurationsL  Diapycnal mixing and advectionLateral eddy mixing and advection 10 10 10 10The greenhouse potential of an N2O molecule is 300 times that of a CO2 molecule.

Nitrous Oxide Fluxes in the Eastern Tropical Atlantic Ocean

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