Summary of Abstract Submission

Abstract Submission No. IO50-02-0006PresentationOral

CHANGES IN CO2 CHEMISTRY IN THE EASTERN EQUATORIAL INDIAN OCEAN SINCE IIOE

Liang Xue*1, Weidong Yu1

1 First Institute of Oceanography, State Oceanic Administration, China

ABSTRACT :

Temporal changes of the CO2 system in the eastern equatorial Indian Ocean are examined using CO2 partial pressure (pCO2) data collected in May 2012, historical pCO2 data since 1962, and total alkalinity (TA) data calculated from salinity. Results show that sea surface pCO2 in the equatorial belt (2N to 2S along 90E and 95E) increased from ~307 atm in April 1963 to ~373 atm in May 1999, ~ 381 atm in April 2007, and ~385 atm in May 2012. The mean rate of pCO2 increase in this area (~1.56 atm yr1) was close to that in the atmosphere (~1.46 atm yr1). Despite the steady pCO2 increase in this region, no significant change in air-sea CO2 fluxes was detected during this period. Ocean acidification indicated by pH and saturation states for carbonate minerals has indeed taken place in this region. Surface pH (total hydrogen scale) and saturation state for aragonite (Ωarag), calculated from pCO2 and TA, decreased significantly at rates of 0.0016 0.0001 yr1 and 0.0095 0.0005 yr1, respectively. We find that the increase in dissolved inorganic carbon (DIC) dominated these changes, while contributions from temperature, salinity, and TA were insignificant. The increase in DIC was most likely associated with the increasing atmospheric CO2 concentration, and the transport of accumulated anthropogenic CO2 from a CO2 sink region via basin-scale ocean circulations. These two processes may combine to drive oceanic DIC to follow atmospheric CO2 increase.