pCO2 is the partial pressure of CO2 in a liquid or gas. In oceanography, it is used to investigate carbon dioxide (CO2) dissolved in the surface layers of the ocean in order to better understand changes in ocean carbon chemistry and ocean acidification due to enhanced atmospheric CO2. The RV Celtic Explorer has a pCO2 Underway System. pCO2 data was collected during the CE18018 (Irish Groundfish Survey legs 2 to 4) survey on board the RV Celtic Explorer in November-December 2018 by the Marine Institute (MI) in the North East Atlantic Ocean. Collect pCO2 data (partial pressure of CO2 in a liquid or gas) to investigate carbon dioxide (CO2) dissolved in the surface layers of the ocean which contributes towards our understand of changes in ocean carbon chemistry and ocean acidification due to enhanced atmospheric CO2.