Sea-air CO2 fluxes in the western Canadian coastal ocean

► We diagnose sea-air CO2 flux variability in the western Canadian coastal ocean. ► Results show greatest CO2 outgassing in autumn across the British Columbia margin. ► Both spring and autumn are the periods of greatest CO2 exchange with the atmosphere. ► Some straits are significant seasonally-persistent atmospheric CO2 source regions. ► We estimate the BC margin is a moderate net annual CO2 sink of −6 mmol m−2 d−1.