Abstract. Deglaciations are characterized by relatively fast and near-synchronous changes in ice sheet volume, ocean temperature, and atmospheric greenhouse gas concentrations, but glacial inceptions occur more gradually. Understanding the evolution of ice sheet, ocean, and atmospheric conditions from interglacial to glacial maximum provides important insight into the interplay of these components of our climate system. Using noble gas measurements in ancient ice samples, we reconstruct mean ocean temperature (MOT) from 74 to 59.5 ka BP, covering the Marine Isotope Stage (MIS) 5-4 boundary, MIS 4, and part of the MIS 4-3 transition. Comparing this MOT reconstruction to previously published MOT reconstructions from the last glacial cycle, we find that the majority of interglacial-glacial ocean cooling occurred across MIS 5, and MOT reached full glacial levels by MIS 4 (−2.7 ± 0.3 °C relative to the Holocene). Comparing MOT to contemporaneous records of CO₂ and benthic 𝛿¹⁸O, we find that ocean cooling and the solubility pump can explain most of the CO₂ drawdown and increase in 𝛿¹⁸O across MIS 5. The timing of ocean warming and cooling in our record indicates that millennial scale climate variability plays a crucial role in setting mean ocean temperature during this interval, as seen during other periods, such as the last deglaciation.

中文翻译：

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海洋同位素第5-4阶段平均海洋温度的演变

摘要。冰川融化的特征是冰盖体积，海洋温度和大气温室气体浓度的变化相对较快且几乎同步，但冰川的始发则更为缓慢。了解冰原，海洋和大气条件从冰间到冰河最大的演变，为深入了解我们气候系统这些组成部分之间的相互作用提供了重要的见识。使用古冰样品中的稀有气体测量，我们将平均海洋温度（MOT）从74到59.5 ka BP重建，覆盖了海洋同位素阶段（MIS）5-4边界，MIS 4和部分MIS 4-3过渡。将此MOT重建与先前发布的上一个冰川周期的MOT重建进行比较，我们发现大部分冰川间冰洋降温发生在MIS 5上 MIS 4使MOT达到了全冰川水平（相对全新世为-2.7±0.3°C）。将MOT与同期CO记录进行比较₂和底栖生物𝛿 ¹⁸ O，我们发现海洋冷却和溶解度泵可以解释MIS 5中大部分CO _2的下降和𝛿 ¹⁸ O的增加。在我们的记录中，海洋变暖和冷却的时间表明千年尺度的气候变化如在其他时期（如最后一次冰消期）所见，在设定此间隔期间的平均海洋温度方面起着至关重要的作用。