The CARIOCA (Carbon Interface Ocean Atmosphere) buoy was anchored at 15 m depth and followed the currents in a quasi-lagrangian way. It was equipped with sensors, namely a spectrophotometer, a thermosalinograph, an optode and a fluorometer, performing hourly measurements of fCO₂, (fugacity of CO₂), SST (Sea Surface Temperature), conductivity, O₂ (oxygen) and fluorescence, at 2 m below the ocean surface, and an anemometer performing atmospheric measurements of wind and atmospheric pressure, at 2 m above the ocean. The data was transmitted in real time via ARGOS.

A three-wavelength spectrophotometer (434, 596 and 830 nm) was used to measure CO₂ fugacity (fCO₂ in μatm). The fCO₂ sensor included an exchanger where a dye solution (thymol blue) was brought into equilibrium with seawater via a semi-permeable CO₂ membrane. Absolute precision of the fCO₂: ± 3 μatm and relative precision: ± 1 μatm.

A thermosalinograph measured the sea surface temperature at 2 m depth, SST in °C, and the conductivity, from which sea surface salinity, SSS in PSS, was derived.

An optode measured dissolved oxygen (O₂ in μmol L^-1). The oxygen measurements of the CARIOCA drifter could not be recalibrated at sea, because unfortunately the O₂ measured by the CTD at the deployment was not calibrated. The oxygen concentration was corrected from temperature and salinity effects and converted to µmol kg^-1. An empirical correction of +8 µmol kg^-1 (which corresponds to the precision of the optode) was applied to bring the values of O₂–O_2sat above zero, during periods of high biological activity. These high biological periods were detected from CARIOCA fluorescence and opposite variations in O₂ and DIC. 

A fluorometer measured the fluorescence (in arbitrary units). To calibrate the measurements of the CARIOCA buoy, in Chl-a units, the SO-CHIC cruise 2022 CTD (DOI 10.17882/95314) and the Seaglider SG675 (10.5281/zenodo.11059425) observations were used.

An anemometer measured the wind speed (m s^-1) and atmospheric pressure (hPa) at 2 m above the sea surface. The wind at 10 m above the ocean was calculated from the wind measurements at 2 m, assuming a neutral atmosphere. The CARIOCA's atmospheric sensor stopped working on the 4 June 2022.