Estimating the Seasonal Carbon Source-Sink Geography of a Natural, Steady-State Terrestrial Biosphere

The seasonal dynamics of biospheric-carbon sources and sinks represents a needed input to global atmospheric CO2 studies and models. For the terrestrial biosphere, initial monthly estimates of overall metabolism and net biosphere-atmosphere carbon flux can be obtained from a steady-state ecological biosphere model. Seasonality is simulated by partitioning annual totals based on bioclimatic relationships. Results are interpolated and quantified geographically. This ecological biosphere model is more geographic, more unified, and more easily parameterized than other biosphere models and provides more mechanistic detail than both atmosphere-based and satellite-based approaches. As a first step, monthly maps of estimated biospheric carbon source and sink regions, as well as estimates of total carbon fluxes (by 10° latitudinal belts), are presented for an equilibrium terrestrial biosphere. These results agree only partly with those of other, mostly simpler modeling approaches. Despite maximum variations of atmospheric CO2 in boreal latitudes, it seems impossible to ignore the enormous contributions of tropical wet-dry regions to global atmospheric CO2 seasonality.