Variability of the Ocean Carbon Cycle in Response to the North Atlantic Oscillation
| Type | Article | ||||||||
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| Date | 2012 | ||||||||
| Language | English | ||||||||
| Author(s) | Keller Kathrin M.1, 2, Joos Fortunat1, 2, Raible Christoph C.1, 2, Cocco Valentina1, 2, Froelicher Thomas L.3, Dunne John P.4, Gehlen Marion5, Bopp Laurent5, Orr James C.5, Tjiputra Jerry6, 7, Heinze Christoph6, 7, Segschneider Joachim8, Roy Tilla9, Metzl Nicolas9 | ||||||||
| Affiliation(s) | 1 : Univ Bern, Inst Phys, CH-3012 Bern, Switzerland. 2 : Univ Bern, Oeschger Ctr Climate Change Res, CH-3012 Bern, Switzerland. 3 : Princeton Univ, Program Atmospher & Ocean Sci, Princeton, NJ 08544 USA. 4 : NOAA GFDL, Princeton, NJ 08540 USA. 5 : Lab Climat & Environm LSCE, F-91191 Gif Sur Yvette, France. 6 : Univ Bergen, Dept Geophys, N-5007 Bergen, Norway. 7 : Bjerknes Ctr Climate Res, N-5007 Bergen, Norway. 8 : Max Planck Inst Meteorol, D-20146 Hamburg, Germany. 9 : Lab Oceanog & Climat LOCEAN IPSL, F-75252 Paris 05, France. |
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| Source | Tellus Series B-chemical And Physical Meteorology (0280-6509) (Co-action Publishing), 2012 , Vol. 64 , P. - | ||||||||
| DOI | 10.3402/tellusb.v64i0.18738 | ||||||||
| WOS© Times Cited | 18 | ||||||||
| Keyword(s) | North Atlantic Oscillation, carbon cycle, ocean biogeochemistry, climate modeling, ocean-atmosphere interaction | ||||||||
| Abstract | Climate modes such as the North Atlantic Oscillation (NAO), representing internal variability of the climate system, influence the ocean carbon cycle and may mask trends in the sink of anthropogenic carbon. Here, utilising control runs of six fully coupled Earth System Models, the response of the ocean carbon cycle to the NAO is quantified. The dominating response, a seesaw pattern between the subtropical gyre and the subpolar Northern Atlantic, is instantaneous (<3 months) and dynamically consistent over all models and with observations for a range of physical and biogeochemical variables. All models show asymmetric responses to NAO+ and NAO− forcing, implying non-linearity in the connection between NAO and the ocean carbon cycle. However, model differences in regional expression and magnitude and conflicting results with regard to air–sea flux and CO2 partial pressure remain. Typical NAO-driven variations are ±10 mmol/m3 in the surface concentration of dissolved inorganic carbon and alkalinity and ±8 ppm in the air–sea partial pressure difference. The effect on the basin-wide air–sea CO2 flux is small due to compensating fluxes on the sub-basin scale. Two models show a reduced carbon sink in the north-eastern North Atlantic during negative NAO phases, qualitatively in accordance with the observed decline during a phase of predominantly negative NAO. The results indicate that wind-driven dynamics are the main driver of the response to the NAO, which – via vertical mixing, upwelling and the associated entrainment of dissolved inorganic carbon and nutrients – leave an imprint on surface pCO2 and the air–sea CO2 flux as well as on biological export production, pH and the calcium carbonate saturation state. The biogeochemical response to the NAO is predominantly governed by vertical exchange between the surface and the thermocline; large-scale horizontal transport mechanisms are of minor importance. | ||||||||
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