Inorganic carbon in the Indian Ocean: Distribution and dissolution processes

TitleInorganic carbon in the Indian Ocean: Distribution and dissolution processes
Publication TypeJournal Article
Year of Publication2002
AuthorsSabine, CL, Key, RM, Feely, RA, Greeley, D
JournalGlobal Biogeochemical Cycles
Date PublishedOct-Nov
ISBN Number0886-6236
Keywordsalkalinity, anthropogenic co2, arabian sea, calcium carbonate, Carbon cycle, dioxide system, dissociation, indian ocean, pressure, saturation state, SEAWATER, Temperature, thermodynamics, total alkalinity, total co2, water

This study uses nearly 25,000 carbon measurements from the WOCE/JGOFS global CO2 survey to examine the distribution of dissolved inorganic carbon (DIC) and total alkalinity (TA) in the Indian Ocean. Shallow and intermediate distributions of inorganic carbon do not strictly follow temperature and salinity because of differing surface gradients and vertical biological processes that work to modify the circulation derived features. Anthropogenic CO2 has increased the shallow DIC by as much as 3%, decreasing the vertical DIC gradient. Deep ocean DIC and TA increase toward the north because of the decomposition and dissolution of organic and inorganic particles. Calcite saturation depths range from 2900-3900 m with the deepest saturation depth in the central Indian Ocean. Variations of aragonite saturation depth (200-1400 m) are similar to calcite, but the deepest saturations are in the southwestern Indian Ocean. The shallowest aragonite saturation depths are found in the Bay of Bengal. In the northern Arabian Sea and Bay of Bengal, the current aragonite saturations are 100 and 200 m shallower, respectively, than in preindustrial times. Estimates of carbonate dissolution rates on isopycnal surfaces range from 0.017 to 0.083 mumol kg(-1) yr(-1) in deep waters. Upper water column dissolution rates range from 0 to 0.73 mumol kg(-1) yr(-1), with a local maximum occurring in intermediate waters just below the aragonite saturation horizon. Dissolution is also generally higher north of the Chemical Front at 10-20degreesS. There is some evidence for significant sedimentary sources in the northern Indian Ocean.