7th Conf. on Atmospheric Chemistry


Possible effects on air pollution of historic and future ocean acidification caused by atmospheric carbon dioxide buildup

Mark Z. Jacobson, Stanford University, Stanford, CA

To date, the effects of ocean acidification due to carbon dioxide buildup on atmospheric chemistry have not been examined. Here, a noniterative, implicit, mass-conserving, unconditionally-stable, positive-definite numerical scheme that solves nonequilibrium air-ocean transfer equations for any atmospheric constituent and time step was derived. The method, referred to as the Ocean Predictor of Dissolution (OPD) scheme, was then coupled with EQUISOLV O, a new ocean chemical equilibrium module based on the EQUISOLV II atmospheric aerosol solver. Here the OPD-EQUISOLV O schemes were used to calculate gas concentrations and ocean composition and pH among dozens of gas and dissolved species in the Na-Cl-Mg-Ca-K-H-O-Li-Sr-C-S-N-Br-F-B-Si-P system. The modules were first integrated into a one-dimensional ocean/two-compartment atmospheric model driven by emission to examine the historic change in atmospheric CO2 and ocean composition from 1751-2004 and the possible future change in CO2 and ocean composition from 2004–2104. CO2 estimates from the historic simulation compare well with the measured CO2 record. Whereas surface ocean pH is estimated to have dropped from near 8.25 to near 8.14 between 1751 and 2004, it is forecasted to decrease to near 7.85 in 2100 under the SRES A1B emission scenario, for a factor of 2.5 increase in H+ in 2100 relative to 1751. This “ocean acidification” is calculated to increase the atmospheric concentrations of non-CO2 atmospheric acids, such as hydrochloric, nitric, and sulfurous acids, but decrease the concentration of the base ammonia. The existence and direction of this effect are almost certain, suggesting that CO2 buildup may have an additional impact on air quality, particularly aerosol particles, near coastal cities; however, the magnitude needs further investigation. .

Session 3, Aerosol Measurements and Radiative Forcing Effects
Tuesday, 11 January 2005, 8:45 AM-12:00 PM

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