δ¹⁸O of benthic foraminifera from sediment core MD01-2444 on the Portuguese Margin, Marine Isotope Stage 3

Benthic foraminifera oxygen isotopes: The benthic isotope record was generated by the late N.J. Shackleton. Measurements were carried out in the Godwin Laboratory for Palaeoclimate Research (University of Cambridge), using a VG PRISM mass spectrometer. Where possible two or three separate analyses of different benthic species were made in each sample; a correction factor was applied according to the species and the average of all the corrected values at each level is shown in the figures. The following species were analysed, and adjusted as indicated: Cibicidoides sp.: +0.51; Uvigerina peregrina and similar specimens: 0.0; Globobulimina affinis: -0.4; Cibicidoides wuellerstorfi, +0.64; Globocassidulina sp.: -0.1; Hoeglundina elegans: -0.7. These adjustments are optimized for this particular core in accordance with the long-standing convention by which Uvigerina peregrina is assumed to deposit oxygen in isotopic equilibrium. Results are reported with reference to the international standard VPDB and the precision is better than ±0.08‰ for d18O. Age model: The age model was developed by aligning the abrupt transitions of d18O record of G. bulloides in core MD01-2444 to warming and cooling events in the NGRIP d18Oice record, presented on: (i) the GICC05 timescale [Svensson, A. et al. A 60,000 year Greenland stratigraphic ice core chronology. Clim. Past 4, 47–57 (2008)]; and (ii) the WD2014: modified timescale, whereby NGRIP GICC05 ice ages 31.2–67.2 ka are multiplied by 1.0063. [Buizert, C. et al. The WAIS Divide deep ice core WD2014 chronology – Part 1: Methane synchronization (68–31 ka BP) and the gas age–ice age difference. Clim. Past 11, 153-173 (2015)].