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JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 112, C09017, doi:10.1029/2006JC003966, 2007

Uptake and spreading of anthropogenic trace gases in an eddy-permitting model of the Atlantic Ocean

Arne Biastoch

Leibniz-Institut für Meereswissenschaften, Kiel, Germany


Christoph Völker

Alfred-Wegener-Institut, Bremerhaven, Germany


Claus W. Böning

Leibniz-Institut für Meereswissenschaften, Kiel, Germany


Abstract

An eddy-permitting circulation model of the Atlantic Ocean was used to study the effect of mesoscale processes on the uptake and spreading of anthropogenic CO2 and CFC-11. A comparison with a coarser-resolution model version shows anthropogenic tracer distributions with qualitatively similar patterns, but much more structure (e.g., stronger longitudinal gradients) in the eddy-permitting model, improving the agreement with observations. The better representation of the formation of water masses such as subpolar-mode water in the eddy-permitting model has an influence on the distribution of anthropogenic CO2 over density classes, but no influence on the total inventory taken up. In the subpolar Atlantic, the air-sea flux of CFC-11 is dominated by deep-water formation, while the air-sea flux of anthropogenic CO2 extends over a larger part of the subpolar gyre and has a clear association with North Atlantic surface currents. An in-depth analysis of the mechanisms shaping this distribution showed that the entrainment of water from below into the mixed layer determines the structure in the subpolar North Atlantic, whereas the temporal correlation between surface heat fluxes and mixed-layer depth is more important in the subtropical gyre. The northward, integrated heat and anthropogenic CO2 transports in midlatitudes are closely correlated on seasonal to interannual timescales. This has implications for using the ongoing monitoring arrays of the thermohaline circulation for estimation of the transport of anthropogenic CO2.

Received 12 October 2006; accepted 2 July 2007; published 20 September 2007.

Index Terms: 4805 Oceanography: Biological and Chemical: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4912); 4520 Oceanography: Physical: Eddies and mesoscale processes; 4534 Oceanography: Physical: Hydrodynamic modeling; 1615 Global Change: Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912).

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Citation: Biastoch, A., C. Völker, and C. W. Böning (2007), Uptake and spreading of anthropogenic trace gases in an eddy-permitting model of the Atlantic Ocean, J. Geophys. Res., 112, C09017, doi:10.1029/2006JC003966.