Various water column variables, including salinity, dissolved inorganic nutrients, pH, total alkalinity, dissolved inorganic carbon, radio-carbon isotopes were measured in samples collected using a Niskin-bottle rosette at selected depths from sites offshore of California and Oregon from October to November 2018 during NOAA cruise SH-18-12 on the R/V Bell M. Shimada (USGS field activity 2018-663-FA). CTD (Conductivity Temperature Depth) data were also collected at each depth that a Niskin-bottle sample was collected and are presented along with the water sample data. This data release supersedes version 2.0, published in September 2021 at https://doi.org/10.5066/P99DIQZ5. Versioning details are documented in the accompanying VersionHistory_P99MJ096.txt file.