It suggests that at the largest spatial

scales, state-of-the-art representations of physical check details processes and assimilation approaches embedded in the reanalysis methods, while quite different among the different reanalyses, produce consistent results. In essence, this means that important variables used for ocean carbon model forcing are similar on global scales, and that whatever important differences there are among the four reanalysis products, global ocean carbon mean fluxes and pCO2 are insensitive to them. This is less sweeping when one considers that only a portion of the vast reanalysis variables produced are important in ocean carbon modeling, the most important of which are surface temperature, wind speeds and stresses, and ice distributions, and when the sensitivities of ocean carbon models are determined by complex interactions in the model formulations. Although the global carbon flux and pCO2 distributions are similar among reanalyses, there are considerable differences on oceanographic basin scales. Air–sea carbon fluxes,

which, as small differences between large values of atmospheric and ocean pCO2, are especially sensitive to small variations in the representation of atmospheric forcing by reanalysis products. None of the reanalysis products are uniformly superior in all basins, nor are any uniformly inferior, as compared to in situ estimates. The differences among the reanalyses are largest in the high latitudes and the tropics, selleck kinase inhibitor which incidentally represent the basins of strongest sinks and strongest sources, respectively. Few of the

major departures observed in MERRA forcing, such as the South Atlantic and Pacific, North not Indian, North Central Pacific, and North Pacific, are rectified by the other reanalysis products (Fig. 5). ECMWF forcing, however, substantially ameliorates the departures observed in the MERRA and NCEP forcings in the North Indian and the Equatorial Pacific. Attribution of the differences of air–sea fluxes to specific variables in the reanalysis products is difficult because of the complexity of the ocean carbon cycle. Additionally, differences in annual mean fluxes shown here can be the result of seasonal differences in reanalysis products. A complete analysis of the effects of the reanalysis products and their influences on the representation of the global ocean carbon cycle is beyond the scope of this paper. However, it is worthwhile to attempt to relate differences in forcing with differences in fluxes, at least at coarse basin and annual scales, to assist in understanding how the reanalysis variables are affecting the observed changes in the representation of the global ocean carbon cycle. First, we note that there are really only 6 reanalysis variables affecting the air–sea fluxes in this biogeochemical model: ice concentrations, SST, surface pressure, wind speeds, and the x and y components of wind stress ( Fig. 1).