Water column baseline assessment for offshore Carbon Dioxide Capture and Storage (CCS) sites: Analysis of field data from the Goldeneye storage complex area

•Environmental monitoring for offshore carbon dioxide storage sites.•Analysis of water column in situ measurements for the determination of baseline conditions at an experimental site for CO2 storage in the North Sea.•Assessment of the variability between carbonate variables and physicochemical parameters at the near seabed for the identification of potential non-natural CO2 emissions at offshore storage sites.