The CO2 instrument used on Tukuma Arctica was new in 2014 and was moved from Nuka Arctica to Tukuma Arctica in 2018. The system provides stable and high quality measurements and consists of an equilibrator, through which seawater is pumped with a flow of about 3L/min. A spiral nozzle forms a regular spray, so that the water and the gas phase achieve equilibriums fast. The gas phase is then pumped through a NDIR analyzer, there the mole fraction of carbon dioxide is measured. From this, the fCO2 is calculated by using the respective sea surface temperature and salinity. Regularly, the system measures four different calibrations gases and the atmospheric CO2 fugacity. Besides the fugacity of carbon dioxide, the sea surface temperature, the sea surface salinity, and disolved oxygen in sea surface are measured. The sea surface salinity and measured by LOCEAN using a SBE21. This data can be found here.