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We reconstructed the past deep-water character of the equatorial Indian Ocean using the isotope ratio of neodymium (εNd) in the Fe–Mn coating of mixed-species foraminifera. When compared with previous εNd records at the same site (ODP 758) and at another site to the west (SK 129), the three datasets were consistent and showed glacial-interglacial variations, even though the other two records were extracted from different media (cleaned foraminifera and bulk sediment leach). This confirms that while the foraminiferal coating is the preferred medium for reconstructing past bottom water εNd records, for carbonate-dominated lithologies, weak acid extraction of bulk sediment is also a viable option offering high-resolution capabilities. When the lithology includes volcanic particles or high organics, the extraction protocol may need to be adjusted to guard against detrital contamination or a slight correction may need to be applied. During glacials, the deep waters bathing the equatorial Indian Ocean had a larger AABW component and during interglacials a larger NADW component. Our HI1808-GPC04 record supplements the ODP 758 record in the interval with prominent AABW signal (MIS 6/5 transition and MIS 7) and reveals regional effects in some non-radiogenic intervals. The smaller differences between the HI1808-GPC04/ODP 758 and SK 129 records seem to reflect regional Nd input from river systems and non-radiogenic Nd from the boundaries.

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The deglacial CO 2 outgassing intervals of the Heinrich Stadial-1 (HS1; 17.5-15 kyr) and the Younger Dryas (YD; 12.9-11.5 kyr) provide key into the oceanographic carbon storage system (Shuttleworth et al., 2020). In the North Pacific (NP; Gray et al., 2018) and East Equatorial Pacific (EEP; Martinez-Boti et al., 2015), a distinct CO 2 outgassing event appears even in late LGM (18-20ka). On the other hand, in the West Equatorial Pacific (WEP; Palmer and Pearson, 2003), the CO 2 content of surface seawater in thewas much lower, so it is difficult to explain WEP pattern .In this study, we present a new high-resolution boron isotopederived pCO 2,sw record for 23-12 ka at Shatsky Rise, North West Pacific (NWP). This area is known as the Kuroshio-Oyashio Extension system, one of the largest surface current mixing areas in the Pacific. Our records were reconstructed from multi-species planktonic foraminifera, each representing water mass at different habitat depths: G. sacculifer (n=21) and G. ruber (n=18) in the tropical-subtropical group, O. universa (n=28) and G. bulloides (n=16) in the open ocean-transition group, and N. Pachyderma (n=26) in the transitional-cold water group.For late LGM (20-18 ka), data from all species indicated high pCO 2,sw (pH 8.0~), the CO 2 source peak appears at the same time as the peaks in NP and EEP. However, in HS1, the behaviors of the tropical-subtropical group and other groups were different, and the signals of EEP and NP were mixed. Through the similarity analysis of these results, we suggest several hypotheses for the NWP carbon storage mechanism along with the Pacific Ocean circulation.

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