Changes in productivity and intermediate circulation in the northern Indian Ocean since the last deglaciation: new insights from benthic foraminiferal Cd / Ca records and benthic assemblage analyses

We have measured Cd/Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate-water circulation and paleo-nutrient cont...

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Bibliographic Details
Published in:Climate of the Past
Main Authors: Ma, Ruifang, Sepulcre, Sophie, Licari, Laetitia, Haurine, Frederic, Bassinot, Franck, Yu, Zhaojie, Colin, Christophe
Format: Report
Language:English
Published: COPERNICUS GESELLSCHAFT MBH 2022
Subjects:
Geology
Meteorology & Atmospheric Sciences
Geosciences
Multidisciplinary
MILLENNIAL-SCALE CHANGES
DEEP SOUTHERN-OCEAN
ARABIAN SEA
ATMOSPHERIC CO2
GLACIAL MAXIMUM
SUMMER MONSOON
BIOLOGICAL PRODUCTIVITY
RADIOCARBON EVIDENCE
WATER CIRCULATION
ATLANTIC CLIMATE
Southern Ocean
Indian
Online Access:http://ir.qdio.ac.cn/handle/337002/179853
https://doi.org/10.5194/cp-18-1757-2022
Description
Summary:We have measured Cd/Ca ratios of several benthic foraminiferal species and studied benthic foraminiferal assemblages on two cores from the northern Indian Ocean (Arabian Sea and northern Bay of Bengal, BoB), in order to reconstruct variations in intermediate-water circulation and paleo-nutrient content since the last deglaciation. Intermediate water Cd-w records estimated from the benthic Cd/Ca reflect past changes in surface productivity and/or intermediate-bottom-water ventilation. The benthic foraminiferal assemblages are consistent with the geochemical data. These results suggest that during the last deglaciation, Cd-w variability was primarily driven by changes in intermediate-water properties, indicating an enhanced ventilation of intermediate-bottom water masses during both Heinrich Stadial 1 and the Younger Dryas (HS1 and YD, respectively). During the Holocene, however, surface primary productivity appears to have influenced Cd-w more than intermediate water mass properties. This is evident during the early Holocene (from 10 to 6 cal ka) when benthic foraminiferal assemblages indicate that surface primary productivity was low, resulting in low intermediate-water Cd-w at both sites. Then, from similar to 5.2 to 2.4 cal ka, surface productivity increased markedly, causing a significant increase in the intermediate-water Cd-w in the southeastern Arabian Sea and the northeastern BoB. The comparison of intermediatewater Cdw records with previous reconstructions of past Indian monsoon evolution during the Holocene suggests a direct control of intermediate-water Cd-w by monsoon-induced changes in upper-water stratification and surface primary productivity.

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