The OISO cruises were initiated in 1998 with the objective of monitoring and understanding the evolution of CO2 in the ocean. Observations are collected once or twice a year onboard R.V. Marion Dufresne in the South Indian and Southern oceans. Such time-series data are crucial in order to: 1) contribute to the annual evaluation of the global carbon budget by regularly feeding international data bases, notably SOCAT and GLODAP; 2) achieve a better understanding of air-sea CO2 flux variability in the South Indian and Southern oceans, with the objective of isolating the anthropogenic perturbation, evaluating the evolution of the oceanic CO2 pump (validation of climate models) and better understanding the mechanisms that drive ocean acidification; 3) document the variability of physical and biological processes that impact the CO2 cycle in the South Indian and Southern oceans; 4) provide in situ observations for the calibration and validation of autonomous observations (e.g., satellite data, Argo, BioArgo and CARIOCA floats, marine mammals equipped with oceanographic sensors); 5) document environmental changes related to climate variability and evaluate the impact on marine organisms (coll., BIAF, MNHN, CEBC).

The OISO26 cruise (coupled to the SOCLIM cruise) aimed at pursuing observations in surface waters (underway) and in the water column (14 stations) between La Reunion and Kerguelen Islands and in the Antarctic zone down to 60°S.