Global core-top ISNW-pH calibration and reconstruction of thermocline seawater carbonate chemistry since 3.8 Ma

Based on the sensitivity of planktonic foraminiferal calcification to ocean acidification, we established a global core‑top calibration between initial size-normalized shell weight (ISNW) of Neogloboquadrina dutertrei and seawater pH, and we reconstructed thermocline pH in the Western Pacific Warm Pool as a tracer of atmospheric pCO2 variability since 3.8 Ma. These core‑top data cover a range of water depths at four locales: (1) the eastern tropical Indian (n = 9), (2) the western tropical Pacific (n = 18), (3) the eastern tropical Pacific (n = 43), and (4) the western tropical Atlantic (n = 16). The sediment core used for thermocline pH and pCO2 reconstructions is Integrated Ocean Drilling Program (IODP) Site U1490, located on the northern edge of the Eauripik Rise at 05°48.95′ N, 142°39.27′ E, with a water depth of 2,341 m.