Abstract. Deglaciations are characterized by relatively fast and; near-synchronous changes in ice sheet volume, ocean temperature, and; atmospheric greenhouse gas concentrations, but glacial inception occurs more; gradually. Understanding the evolution of ice sheet, ocean, and atmosphere; conditions from interglacial to glacial maximum provides insight into the; interplay of these components of the climate system. Using noble gas; measurements in ancient ice samples, we reconstruct mean ocean temperature; (MOT) from 74 to 59.7 ka, covering the Marine Isotope Stage (MIS) 5a–4; boundary, MIS 4, and part of the MIS 4–3 transition. Comparing this MOT; reconstruction to previously published MOT reconstructions from the last and; penultimate deglaciation, we find that the majority of the last; interglacial–glacial ocean cooling must have occurred within MIS 5. MOT; reached equally cold conditions in MIS 4 as in MIS 2 (−2.7 ± 0.3 ∘C relative to the Holocene, −0.1 ± 0.3 ∘C; relative to MIS 2). Using a carbon cycle model to quantify the CO2 solubility pump, we show that ocean cooling can explain most of the; CO2 drawdown (32 ± 4 of 40 ppm) across MIS 5. Comparing MOT to; contemporaneous records of benthic δ18O, we find that ocean cooling; can also explain the majority of the δ18O increase across MIS 5 (0.7 ‰; of 1.3 ‰). The timing of ocean warming and cooling in; the record and the comparison to coeval Antarctic isotope data suggest an; intimate link between ocean heat content, Southern Hemisphere high-latitude climate,; and ocean circulation on orbital and millennial timescales.;
