The underway surface and atmospheric CO2 levels were measured in the west Arctic Ocean during the 6th Chinese National Arctic Research Expedition (CHINARE2014) from 2014-07-27 to 2014-09-09. The system was monitored and calibrated with three certified gas standards and a zero gas every 3 hours. The dataset was reduced by the MatLab program pCO2 Sys v126, following the procedure in Pierrot et al. (2009). This dataset includes measurements of fugacity of CO2 (fCO2) in sea water at sea water temperature, fugacity of CO2 (fCO2) in atmosphere, sea surface temperature, sea surface salinity, atmospheric pressure, and delta fCO2 between sea water and atmosphere (fCO2w - fCO2a). (FR)