Variability of the past deep-water masses in the Arabian Sea over the last 41ka

19 July 2026

Shukla and colleagues (2026, see reference below) propose a high-resolution (∼400-year) authigenic Ɛ_Nd record measured from a sediment core (hereafter referred to as GC10; 2,055 m water depth) located in the eastern Arabian Sea. They demonstrate that variations in the Ɛ_Nd record in this area resulted from changes in the relative proportions of southern-sourced deep-water masses, with Antarctic Bottom Water (AABW) dominating during colder periods and North Atlantic Deep Water (NADW) during warmer periods. On millennial timescales, the same balance between NADW and AABW is observed: whereas the Last Glacial Maximum and Heinrich events are characterized by greater intrusion of AABW, rapid warm climate events show a predominance of NADW. Through analysis of the Nd signature in the lithogenic material, the authors also detect a significant Ganga–Brahmaputra influence between 28 and 18 ka, likely related to an intensified northeast monsoon period.

**Figure**: Bathymetry map of the Indian Ocean with core locations and pathways of different water masses (brown arrows). Location of the present studied CoreSSD60‐GC10 lies in the South Eastern Arabian Sea, marked with a red star. Core SK129‐CR2 and Core SK221‐05 are shown for reference. Filled blue circles denote the seawater sampling stations. Light orange arrows shows the aeolian dust influx from the nearby continents (Bikkina et al., 2023). CDW: Circumpolar Deep Water; AABW: Antarctic Bottom Water; MNADW: Modified North Atlantic Deep Water; RSW: Red Sea Water; PGW: Persian Gulf Water;OFZ: Owen Fracture Zone; LB: Lakshadweep Basin.

Figure: Temporal variation of authigenic (HAc leachates) and detrital Ɛ_Nd values (a) and median grain size (D₅₀) (b) of the present study compared with δ¹⁸O_carbVPDB (Oxygen isotope measured in the Carbonate and expressed relative to Vienna PeeDee Belemnite) (c) and, δ¹⁸O of NGRIP ice core (d), marked with the cold and warm climatic events/periods. Numbers indicate the Dansgaard‐Oeschger interstadials. The red color line shows the 5‐point moving average of δ¹⁸O of the NGRIP core. Radiocarbon (¹⁴C) dates of the GC10 core are marked on the X‐axis with gray diamonds.

Reference:

Shukla, A., Mishra, T. K., & Singh, S. K. (2026). Tracking the Millennial Scale Variability of Deep Water Circulation and Lithogenic Influence in the Arabian Sea Over the Past 41 ka Through Nd Isotope. Paleoceanography and Paleoclimatology, 41. Access the paper:10.1029/2025pa005310

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