These data are in association with a study conducted in the Santa Barbara Basin, California, USA that were used to develop a 20th century record of ocean acidification in the California Current Ecosystem. These data are based on the planktonic foraminifera species G. bulloides' shell characteristics, specifically area-normalized shell weight (ANSW) and include core the individual data used to calculate sample averages.Additional information on collection of ANSW data can be obtained in Osborne et al., (2016) publication in Paleoceanography (doi:10.1002/2016PA002933).