(Table S1) Age determination of sediment cores of the Ontong Java Plateau

We present a reconstruction of deep-water carbonate saturation state (Delta [CO3]2-) in the western equatorial Pacific for the Last Glacial Maximum (LGM) and deglaciation based on changes in the Mg/Ca ratio of planktic foraminifers with increased water depth. Our data suggest there have been changes in bottom waterDelta [CO3]2- over the past 25,000 years at water depths as shallow as 1.6 km. The Delta [CO3]2- reconstruction for the LGM suggests Delta [CO3]2- was similar or slightly higher than modern values between 1.6 and 2.0 km, shifting sharply to lower values (an average ~30 µmol/kg lower) below 2.5 km. The shift in chemistry between 2.0 and 2.5 km supports a hypothesis that Pacific overturning circulation occurred deeper during the LGM with a slightly more ventilated water mass above 2.0 km. The data are not consistent with enhanced preservation in this region of the deep Pacific at depths greater than 2.5 km, suggesting that the long-held view of better preservation throughout the glacial deep Pacific must be reevaluated. For the deglaciation, we have evidence of a Delta [CO3]2- maximum that suggests enhanced deglacial preservation between 1.6 and 4.0 km in comparison to the Holocene and the LGM. The deglacial Delta [CO3]2- was as much as 28 µmol/kg higher than modern between 1.6 and 4.0 km. Results suggest carbonate burial rates were 1.5 times greater during the deglacial than the over the past 5 kyr.本研究基于不同水深浮游有孔虫（planktic foraminifers）的Mg/Ca比值变化，重建了末次冰盛期（Last Glacial Maximum, LGM）与冰消期西赤道太平洋的深水碳酸根离子浓度差值（Delta [CO3]2-，Δ[CO₃²⁻]）。研究数据显示，过去25000年间，水深低至1.6 km的底层水Δ[CO₃²⁻]已发生显著变化。针对末次冰盛期的Δ[CO₃²⁻]重建结果表明，1.6~2.0 km水深区间内的底层水Δ[CO₃²⁻]与现代值相近或略高；而2.5 km以深的水体Δ[CO₃²⁻]则骤降至更低水平，平均较现代低约30 μmol/kg。2.0~2.5 km水深区间内的水化学性质转变，支持了"末次冰盛期太平洋翻转环流深度更深，且2.0 km以浅水体的通风程度略高"这一假说。本研究数据与"西太平洋深水区2.5 km以深区域碳酸盐保存作用增强"的观点不符，这意味着学界长期以来认为"冰期全球深海太平洋碳酸盐保存状况更优"的结论需要重新评估。在冰消期阶段，我们观测到Δ[CO₃²⁻]的峰值信号，表明1.6~4.0 km水深区间内的冰消期碳酸盐保存作用相较于全新世（Holocene）与末次冰盛期均有所增强。1.6~4.0 km水深区间内，冰消期的Δ[CO₃²⁻]较现代最高可高出28 μmol/kg。研究结果显示，冰消期的碳酸盐埋藏速率较过去5000年提升了1.5倍。