Jurnal Internasional A 16 kyr record of ocean circulation and monsoon intensification from the central Bay of Bengal – Naik – – Geochemistry, Geophysics, Geosystems

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The monsoonal signal dominates most climate records from the Indian Ocean. As a consequence, conventional stable isotope tracers have not been effective at tracking ocean circulation in the Indian Ocean, and distinguishing between monsoonal and ocean circulation changes in the Bay of Bengal. Here we present a deglacial through Holocene Nd isotope record of seawater in the central Bay of Bengal, spanning the last 16 kyr. Comparison with a published record from the deep equatorial Indian Ocean (Piotrowski et al., 2009) shows that Nd isotope ratios of these cores were similar until ~8 ka (ƐNd= ‐7 to ‐8 until ~13 ka, and ‐8.5 to ‐9.5 between ~13 and 8 ka), after which the Bay of Bengal record diverges to lower values (ƐNd= ~ ‐10.5). We interpret the Nd isotope record until ~8 ka in both cores to represent the influence of the global overturning ocean circulation. The divergence of the record in the Bay of Bengal since ~8 ka to lower ƐNd‐values is coincident with a major increase in the strength of the rain‐bearing southwest monsoon, and a high sediment load from the Ganga‐Brahmaputra Rivers to the Bengal Fan that reflects major impacts from the intensified monsoon. Thus the Nd isotopes are sensitive recorders of the changes in monsoon intensity in the Bay of Bengal.

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