Carbon dioxide partial pressure (pCO2) and total dissolved inorganic carbon (TCO2) measurements were made on seawater collected from 12 depths at oceanographic station QU39 in the northern Strait of Georgia approximately every two weeks from January 2016 to December 2023. These data were collected as part of the Hakai Institute’s objective to report on patterns of ocean acidification in coastal British Columbia. Temperature, salinity, and pressure data were also captured using CTD profilers (either Sea-Bird Electronics or RBR units following best practices) at the time of seawater collection, and profile data was extracted for the depth at which Niskin bottles were tripped. Sampling depth was determined by calibrated line meter on the research vessel or RBR Solo pressure sensors attached to the Niskin bottle. Samples were fixed at the time of collection using 80 µl of mercuric chloride aboard the Hakai Institute’s research vessel. Temperature and salinity were determined at the time of sample analysis at the Quadra Island Field Station (QIFS) using NIST traceable thermometers (VWR PN 23609-176) and a YSI MultiLab 4010-1 with a MultiLab IDS 4310 conductivity and temperature probe. The YSI probe was calibrated using certified reference materials of known salinity prior to seawater sample analysis. For detailed protocols on sample collection and data processing, including CO2 system determination, please see Campbell et al. (2023; https://doi.org/10.21966/1.521066).