Résumé
This report presents the experimental data obtained during the INDIVAT-1 (Indien Valorisation de Transit) and INDIGO (Indien Gaz Ocean)/INDIVAT-3 expeditions conducted in the Indian Ocean in the late austral winter (July) of 1984, and in the austral summer (Feb.-March) of 1985, respectively. The objectives of the expeditions were to quantify the oceanic penetration of excess CO sub(2) by using carbonate data directly in order to understand thereby the carbon cycle. The individual expeditions are outlined, the experimental techniques are described, and the data are given in tables. The preliminary results show that the surface pH and normalized nitrate, alkalinity, and total CO sub(2) values correlate linearly with temperature; small deviations from linearity are related to the subtropical front and the equatorial upwelling. Large variations in nitrate are found in surface waters collected at the same stations but in different seasons; however, there is less variation between normalized nitrate concentrations in waters with the same temperature. A seasonal difference in alkalinity and total CO sub(2) seems to exist even when compared at the same salinity and temperature. The decrease in alkalinity and total CO sub(2) between the Antarctic Ocean and the Indian central water found north of the subtropical front can be attributed tentatively to the decrease in nitrate and the increase in temperature. The remnant North American deep water (NADP), which has a very low alkalinity, is clearly identified by pH and total CO sub(2) data; nutrient, oxygen, and calcium data also help in tracing NADP. The alkalinity and total CO sub(2) data for subsurface waters obtained in these expeditions are in good agreement with GEOSECS data for GS 427 and 428, but not for GS 429.