Quantifying the drivers of ocean‐atmosphere CO2 fluxes. Issue 7 (6th July 2016)

• Record Type: Journal Article
• Authors: Lauderdale, Jonathan M.; Dutkiewicz, Stephanie; Williams, Richard G.; Follows, Michael J.
• Is Part Of: Global biogeochemical cycles. Volume 30:Issue 7(2016:Jul.)
• Page Start: 983
• Page End: 999
• Publication Date: 2016-07-06
• Subjects: air‐sea flux -- carbon dioxide -- regional drivers; Biogeochemical cycles -- Periodicals; Electronic journals; 577.1405
• DOI: 10.1002/2016GB005400
• Languages: English
• ISSNs: 0886-6236

Abstract

Abstract: A mechanistic framework for quantitatively mapping the regional drivers of air‐sea CO2 fluxes at a global scale is developed. The framework evaluates the interplay between (1) surface heat and freshwater fluxes that influence the potential saturated carbon concentration, which depends on changes in sea surface temperature, salinity and alkalinity, (2) a residual, disequilibrium flux influenced by upwelling and entrainment of remineralized carbon‐ and nutrient‐rich waters from the ocean interior, as well as rapid subduction of surface waters, (3) carbon uptake and export by biological activity as both soft tissue and carbonate, and (4) the effect on surface carbon concentrations due to freshwater precipitation or evaporation. In a steady state simulation of a coarse‐resolution ocean circulation and biogeochemistry model, the sum of the individually determined components is close to the known total flux of the simulation. The leading order balance, identified in different dynamical regimes, is between the CO2 fluxes driven by surface heat fluxes and a combination of biologically driven carbon uptake and disequilibrium‐driven carbon outgassing. The framework is still able to reconstruct simulated fluxes when evaluated using monthly averaged data and takes a form that can be applied consistently in models of different complexity and observations of the ocean. In this way, the framework may reveal differences in the balance of drivers acting across an ensemble of climate model simulations or be applied to an analysis and interpretation of the observed, real‐world air‐sea flux of CO2 . Key Points: We have developed a quantitative framework for diagnosing regional drivers of air‐sea CO2 fluxes Components can be evaluated in a model or can be derived from operational data, climatologies, and ocean state estimates Model CO2 fluxes result from a balance between air‐sea heat fluxes, biological activity, and disequilibrium