Find in Library

<p>We have measured <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Cd</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="36pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="fa6d952d4ad79a0e5bb60124833d0a90"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-18-1757-2022-ie00003.svg" width="36pt" height="14pt" src="cp-18-1757-2022-ie00003.png"/></svg:svg></span></span> 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<span class="inline-formula">_w</span> records estimated from the benthic <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M4" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">Cd</mi><mo>/</mo><mi mathvariant="normal">Ca</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="36pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="356d91f762abb1c494ff56849a7f2a6a"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cp-18-1757-2022-ie00004.svg" width="36pt" height="14pt" src="cp-18-1757-2022-ie00004.png"/></svg:svg></span></span> 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<span class="inline-formula">_w</span> 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<span class="inline-formula">_w</span> 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<span class="inline-formula">_w</span> at both sites. Then, from <span class="inline-formula">∼</span> 5.2 to 2.4 cal ka, surface productivity increased markedly, causing a significant increase in the intermediate-water Cd<span class="inline-formula">_w</span> in the southeastern Arabian Sea and the northeastern BoB. The comparison of intermediate-water Cd<span class="inline-formula">_w</span> records with previous reconstructions of past Indian monsoon evolution during the Holocene suggests a direct control of intermediate-water Cd<span class="inline-formula">_w</span> by monsoon-induced changes in upper-water stratification and surface primary productivity.</p>