Abstract Whether the Indian Summer Monsoon (ISM) Maximum started in the early Holocene or middle Holocene remains a controversial issue. Grain-size measurements were conducted on 157-cm-long core ADM-C1 from the Andaman Sea; the core spanned the last 11.2 kyr BP. Four end-members (EMs) were unmixed using lognormal parametric end-member modeling. Genetic analyses of the grain-size EMs suggested the EM1 and EM2 may correlate with suspension in the upper layers and transportation in the benthic nepheloid layer, respectively, while the EM3 and EM4 were tied with deposition affected by monsoonal currents and sedimentation under extreme events, respectively. The EM3 was dominated by ISM intensity and transported by summer monsoon currents, with increase in the proportion of EM3 reflecting increasing ISM intensity, and vice versa. Variations in EM3 were used to define three stages of ISM evolution, as follows: (1) During 11.2–9.1 kyr BP, EM3 was relatively low, indicating a weak ISM; (2) during 9.1–4.5 kyr BP, EM3 increased substantially, indicating a strengthened ISM; (3) during 4.5-0 kyr BP, EM3 decreased gradually, suggesting a gradual weakening of the ISM. The Holocene ISM Maximum started at ∼9.1 kyr BP rather than in the early Holocene, which may have been partly due to the slowdown of the Atlantic meridional overturning circulation (AMOC) during the early Holocene that resulted in a decreased land-sea thermal contrast between the landmass and the Indian Ocean. An additional cause may have been the remnant Northern Hemisphere ice sheets that impeded the northward shift of the Intertropical Convergence Zone (ITCZ). Seven relatively brief decreases in the ISM intensity (events 7, 6, 5, 4, 3, 2, 1) occurred at ca. 10.3, 9.7, 7.3, 5.7, 4.2, 2.4, and 0.8 kyr BP, respectively. They corresponded, within the age uncertainties, to the increased supplies of ice-rafted detritus to North Atlantic sediments, implying that changes in the ISM intensity on millennial scale were dominated by climatic processes in northern high latitudes.

中文翻译：

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从安达曼海沉积物粒度端元模型推断的全新世印度夏季风变化

摘要 印度夏季风（ISM）极大期是从全新世早期还是全新世中期开始，仍存在争议。晶粒尺寸测量是在来自安达曼海的 157 厘米长的 ADM-C1 岩芯上进行的；核心跨越了最后的 11.2 kyr BP。使用对数正态参数端元建模对四个端元 (EM) 进行分离。粒度EMs的遗传分析表明，EM1和EM2可能分别与上层悬浮和底栖云母层运输相关，而EM3和EM4与受季风流影响的沉积和极端事件下的沉积有关，分别。EM3 以 ISM 强度为主，受夏季风流的输送，EM3 比例增加反映 ISM 强度增加，反之亦然。EM3 的变化被用来定义 ISM 演化的三个阶段，如下： (1) 在 11.2-9.1 kyr BP 期间，EM3 相对较低，表明 ISM 较弱；(2) 在 9.1-4.5 kyr BP 期间，EM3 显着增加，表明 ISM 增强；(3) 在 4.5-0 kyr BP 期间，EM3 逐渐下降，表明 ISM 逐渐减弱。全新世 ISM 最大值开始于约 9.1 kyr BP 而不是全新世早期，这可能部分是由于全新世早期大西洋经向翻转环流 (AMOC) 的放缓导致海陆之间的海陆热对比降低。大陆和印度洋。另一个原因可能是北半球残留的冰盖阻碍了热带辐合带（ITCZ）向北移动。ISM 强度（事件 7、6、5、4、3、2、1）发生了七次相对短暂的下降。分别为 10.3、9.7、7.3、5.7、4.2、2.4 和 0.8 kyr BP。在年龄不确定性内，它们对应于北大西洋沉积物的冰筏碎屑供应增加，这意味着千年尺度上 ISM 强度的变化主要由北部高纬度的气候过程主导。