Glacial expansion of carbon-rich deep waters into the Southwestern Indian Ocean over the last 630 kyr Pérez Asensio, José Noel Tachikawa, Kazuyo Vidal, Laurence De Garidel-Thoron, Thibault Sonzogni, Corinne Guihou, Abel Deschamps, Pierre Jorry, Stéphan J. Chen, Min-Te Carbon cycle Neodymium isotopes Carbon isotopes Glacial-interglacial cycles Pleistocene Indian Ocean JNPA was funded by the INDEXCLIMA project. This project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement N°840675. Nd isotopic analyses were measured on Neptune+ MC-ICPMS acquired in the frame of EQUIPEX ASTER-CEREGE project. We also thank the support of the INSU-LMC14 national laboratory for ARTEMIS radiocarbon dating for samples from core MD96-2052 and the INSU-LEFE-CLIMOZA project for stable isotope analyses from core MD96-2052. Marta Garcia for her technical support with ICP-MS Nd concentration measurements and Hélène Mariot for her careful maintenance of the clean laboratory are thanked. MiSo received support from the French National Programme LEFE (Les Enveloppes Fluides et l'Environnement) and from the French government under the France 2030 investment plan, as part of the Initiative d'Excellence d'Aix-Marseille Université - A*MIDEX (AMX-19-IET-012) and from the Research Federation ECCOREV (FR 3098; Aix-Marseille Univ., CNRS, INRAE, IRSN, CEA, Univ. Toulon, Univ. Avignon, Univ. Nimes). Oceanic carbon storage is one of the main sinks for atmospheric CO2, and thought to be the major contributing factor for CO2 drawdown during past glacial periods. Both physical and biogeochemical processes control the capacity of carbon storage in the ocean. During glacial periods of the Pleistocene the larger volume of deep-water masses of Southern Hemisphere origin in the Atlantic has been shown to promote carbon storage in the Southern Ocean. However, the latitudinal extension of this water mass in the Indian Ocean has been scarcely studied. In this study, we combine foraminiferal εNd and benthic δ13C of two sediment cores in the southwest Indian Ocean (MD96–2077, 33◦S, 3781 m water depth; MD96–2052, 19◦S, 2627 m water depth), to reconstruct the spatial and temporal evolution of glacial carbon-rich deep waters in the SW Indian over the last 630 kyr. The combined use of foraminiferal εNd and benthic δ13C allows to distinguish δ13C changes related to water mass mixing and from respired carbon accumulation within the water masses. Nutrient-rich deep waters, which cannot be explained by the enhanced proportion of southern-sourced waters, were present at core sites deeper than 2700 m during glacial periods and extended at least until 33◦S into the SW Indian Ocean. From Marine Isotope Stage (MIS) 14 to MIS 10, glacial carbon storage increased gradually until reaching its highest capacity during the extreme glacial periods MIS 12 and 10. Orbital forcing (100-kyr eccentricity, 41-kyr obliquity), restricted air-sea exchange and enhanced ocean stratification, fostered higher carbon storage during periods of relatively lower eccentricity and obliquity. Furthermore, after MIS 10, a progressive transition was observed from 100-kyr eccentricity to 41-kyr obliquity cycles in benthic δ13C and δ18O records of core MD96–2077 and sea-ice cover changes derived from icerafted debris of the Agulhas Plateau composite core site. 2024-09-27T07:37:08Z 2024-09-27T07:37:08Z 2023-11 journal article J.N. Pérez-Asensio et al. Glacial expansion of carbon-rich deep waters into the Southwestern Indian Ocean over the last 630 kyr. Global and Planetary Change 230 (2023) 104283. https://doi.org/10.1016/j.gloplacha.2023.104283 https://hdl.handle.net/10481/95192 10.1016/j.gloplacha.2023.104283 eng info:eu-repo/grantAgreement/EC/H2020/840675 http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Elsevier