Circumpolar Deep Water variability in the Southern Ocean during the past 500 ka

The Circumpolar Deep Water (CDW) is one of the key components of the global climate system and Antarctic cryosphere. However, the variability of the CDW in the Indian sector of the Southern Ocean over glacial-interglacial climate cycles is still unknown due to a lack of knowledge of deep-water geochemistry. The new records of δ¹⁸O and δ¹³C in benthic foraminifer from Del Caño Rise (DCR-1PC and DCR-2PC) characterized the δ¹³C composition of CDW in the Indian sector of the Southern Ocean. During the glacial periods, the South Indian has lower δ¹³C values, representing the influence of a more southern water mass, perhaps a glacial Antarctic Bottom Water (AABW). A comparison with published South Atlantic (ODP 1090) and South Pacific (PS 75/59) deep water records suggests a continuous water mass exchange throughout the past 500 ka. Almost identical glacial-interglacial δ¹³C variations imply a common deep-water evolution in all basins, suggesting persistent CDW exchange and homogenization. A much lower δ¹³C signal was observed at the deeper Cape Basin (ODP 1089, RN13-229), which was influenced by strong AABW originating from the Weddell Sea during the glacial periods. The anomalous heavier values (> 0.5‰) were recorded at DCR-1PC during the MIS 5 (~97 ka and ~83 ka), suggesting the strong influence of the North Atlantic Deep Water (NADW).