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The air‐water CO 2 exchange of a coastal sea—A sensitivity study on factors that influence the absorption and outgassing of CO 2 in the B altic S ea
Author(s) -
Gustafsson Erik,
Omstedt Anders,
Gustafsson Bo G.
Publication year - 2015
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
eISSN - 2169-9291
pISSN - 2169-9275
DOI - 10.1002/2015jc010832
Subject(s) - alkalinity , dissolved organic carbon , environmental science , outgassing , phytoplankton , nutrient , total inorganic carbon , carbon dioxide , forcing (mathematics) , seawater , atmospheric sciences , carbon cycle , environmental chemistry , chemistry , oceanography , ecology , geology , ecosystem , organic chemistry , biology
In this study, the BALTSEM model is used to estimate how air‐water CO 2 fluxes in the Baltic Sea respond to parameterizations of organic alkalinity (A org ), gas transfer, and phytoplankton growth, and further to changes in river loads. The forcing data include the most complete compilation of Baltic river loads for dissolved inorganic and organic carbon (DIC and DOC) and total alkalinity (TA). In addition, we apply the most recent estimates of internal TA generation in the system. Our results clearly demonstrate how air‐water CO 2 fluxes of a coastal sea depend on river loads of carbon, TA, and nutrients as well the freshwater import itself. Long‐term changes in DIC loads are shown to be compensated by corresponding changes in air‐water CO 2 exchange. By adding A org , a discrepancy in the carbonate system calculations was removed, and the simulated net CO 2 absorption of the system decreased by 11%. A new parameterization for cyanobacteria growth significantly improved the seasonal development of pCO 2 in the central Baltic Sea, although the net effect on CO 2 fluxes was below 5%. By applying either a linear, quadratic, or cubic wind speed dependence for gas transfer, the long‐term net CO 2 exchange was adjusted by less than 5%. There is no clear indication that any one of these parameterizations provides a more accurate estimate of CO 2 fluxes than the other two. Our findings are applicable in other coastal areas that are heavily influenced by river loads of TA, DIC, and DOC.