Impact of oceanic circulation on biological carbon storage in the ocean and atmospheric pCO2
Figure S1: Atmospheric pCO2 versus surface PO4 south of 30°S, and globally averaged preformed PO4. (18.42Kb)
Figure S2: Atmospheric pCO2 versus surface PO4 and globally averaged preformed PO4. Similar to Figure 1 but includes a wider range of simulations. (27.12Kb)
Text S1: The auxiliary material confirms through an additional set of simulations that the functional relationship between globally averaged preformed PO4 and atmospheric pCO2 is robust and predictive. (88.47Kb)
Sarmiento, Jorge L.
Toggweiler, J. R.
Follows, Michael J.
Mignone, B. K.
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We use both theory and ocean biogeochemistry models to examine the role of the soft-tissue biological pump in controlling atmospheric CO2. We demonstrate that atmospheric CO2 can be simply related to the amount of inorganic carbon stored in the ocean by the soft-tissue pump, which we term (OCS soft ). OCS soft is linearly related to the inventory of remineralized nutrient, which in turn is just the total nutrient inventory minus the preformed nutrient inventory. In a system where total nutrient is conserved, atmospheric CO2 can thus be simply related to the global inventory of preformed nutrient. Previous model simulations have explored how changes in the surface concentration of nutrients in deepwater formation regions change the global preformed nutrient inventory. We show that changes in physical forcing such as winds, vertical mixing, and lateral mixing can shift the balance of deepwater formation between the North Atlantic (where preformed nutrients are low) and the Southern Ocean (where they are high). Such changes in physical forcing can thus drive large changes in atmospheric CO2, even with minimal changes in surface nutrient concentration. If Southern Ocean deepwater formation strengthens, the preformed nutrient inventory and thus atmospheric CO2 increase. An important consequence of these new insights is that the relationship between surface nutrient concentrations, biological export production, and atmospheric CO2 is more complex than previously predicted. Contrary to conventional wisdom, we show that OCS soft can increase and atmospheric CO2 decrease, while surface nutrients show minimal change and export production decreases.
Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 22 (2008): GB3007, doi:10.1029/2007GB002958.
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