Interannual properties of the CO2 system in the Southern Ocean south of Australia

Abstract

AbstractIn order to quantify the temporal variations of ocean properties, the MINERVE programme was designed to perform time-series measurements in the Southern Indian Ocean south of Australia. In the sub-Antarctic region (SAR, 48.5 ± 6.0°S), the mean CO2 flux increased from spring to summer from -6.8 mmol.m-2.d-1 in October 2005 to -9.9 mmol.m-2.d-1 in February 2006. In the Permanent Open Ocean Zone (POOZ, 57.5 ± 3.0°S), we observed lower pCO2 in summer than in spring (340 and 398 μatm, respectively). The mean CO2 flux showed large temporal variations from -0.2 mmol.m-2.d-1 in October 2005 to -8.2 mmol.m-2.d-1 in February 2006. The large temporal variation was associated with increased phytoplankton biomass. In the Continental Antarctic Zone (66.0 ± 1.0°S), the mean CO2 flux decreased from +14.9 mmol.m-2.d-1 in October 2005 to -8.4 mmol.m-2.d-1 in February 2006. In winter and spring, deep water mixing and seasonal sea-ice strongly increase pCO2sea above atmospheric level. In contrast, during summer, the effect of biological CO2 uptake decreased pCO2sea. Furthermore, these data allowed us to parameterize AT and CT as a function of temperature and salinity.