Description: The dataset compiles reconstructed changes in bottom water temperature and global ice volume from 0 to 17 Ma using δ18O in conjunction with Mg/Ca records of the infaunal benthic foraminifer, O. umbonatus from Ocean Drilling Program (ODP) Site 130-806 (equatorial Pacific; ~2500 m). This dataset covers the middle Miocene to present (17-0 Ma) and has an average temporal resolution of ~0.2 Ma. Application of the new equations to the Site 130-806 record leads to the suggestion that global ice volume was greater than today after the Middle Miocene Climate Transition (~14 Ma). ODP Site 130-806 bottom waters cooled and freshened as the Pacific zonal sea surface temperature gradient increased, and climate cooled through the Pliocene, prior to the Plio‐Pleistocene glaciation of the Northern Hemisphere.

Description: The Mg/Ca of planktic foraminifera Globigerinoides ruber (white) is a widely applied proxy for tropical and sub-tropical sea-surface temperature. The accuracy with which temperature can be reconstructed depends on how accurately relationships between Mg/Ca and temperature and the multiple secondary controls on Mg/Ca are known; however, these relationships remain poorly quantified under oceanic conditions. Here, we present new calibrations based on 440 sediment trap/plankton tow samples from the Atlantic, Pacific and Indian Oceans, including 130 new samples from the Bay of Bengal/Arabian Sea and the tropical Atlantic Ocean. Our results indicate temperature, salinity and the carbonate system all significantly influence Mg/Ca in G. ruber (white). We propose two calibration models: The first model assumes pH is the controlling carbonate system parameter. In this model, Mg/Ca has a temperature sensitivity of 6.0 ± 0.8 %/°C (2 Sigma), a salinity sensitivity of 3.3 ± 2.2%/PSU and a pH sensitivity of -8.3 ± 7.7%/0.1 pH units; The second model assumes carbonate ion concentration ([CO3**2-]) is the controlling carbonate system parameter. In this model, Mg/Ca has a temperature sensitivity of 6.7 ± 0.8%/°C, a salinity sensitivity of 5.0 ± 3.0%/PSU and a [CO3**2-] sensitivity of -0.24 ± 0.11/µmol kg**1. In both models, the temperature sensitivity is significantly lower than the widely-applied sensitivity of 9.0 ± 0.6%/°C. Application of our new calibrations to down-core data from the Last Glacial Maximum, considering whole ocean changes in salinity and carbonate chemistry, indicate a cooling of 2.4 ± 1.6 °C in the tropical oceans if pH is the controlling parameter and 1.5 ± 1.4 °C if [CO3**2-] is the controlling parameter.