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末次冰消期以来印度半岛南部岸外沉积历史及其对印度沿岸流演化的指示
康晓莹
Subtype硕士
Thesis Advisor于兆杰
2024-05
Degree Grantor中国科学院大学
Place of Conferral中国科学院海洋研究所
Abstract

印度沿岸流是推动孟加拉湾和阿拉伯海之间物质交换的主要洋流,重建其过去演化历史对于预测未来北印度洋海洋环境变化至关重要。然而,目前关于其过去历史的研究极少,几乎空白。本文展示了印度南部海域MD77-191岩芯的黏土矿物和粒度记录,并结合瞬变气候模型,以追溯自末次冰消期以来印度沿岸流演化历史。结合已发表的锶-钕同位素结果,认为MD77-191岩芯的沉积物主要来自阿拉伯海和孟加拉湾沉积物的混合,而印度沿岸流是主要的沉积物搬运者。夏季风盛行期间,印度沿岸流由阿拉伯海流向孟加拉湾,沉积物主要为阿拉伯海来源,此时蒙脱石/(伊利石+绿泥石)比值较高;反之,冬季风盛行期间,印度沿岸流由孟加拉湾流向阿拉伯海,沉积物主要为孟加拉湾来源,蒙脱石/(伊利石+绿泥石)比值降低。结合瞬变气候模型结果,推断北印度洋大气环流格局变化导致的印度季风转向是主要驱动因素。另外,岩芯MD77-191的粒度和端元模拟结果显示:189.5 kyr的冰消期,印度冬季风较强,到达MD77-191站位的阿拉伯海沉积物较孟加拉湾沉积物更粗;而9.5 ka至今,以上现象反向变化,阿拉伯海沉积物较孟加拉湾沉积物更细。推测海平面变化导致阿拉伯海东侧广阔陆架沉积物的粗细变化可能是主要原因,而赤道印度洋偶极子模态转型影响的印度夏季风变化是次要原因。

本文首次提供了末次冰消期以来具有精确定年的北印度洋边缘海物质交换的连续沉积记录,揭示了大尺度大气环流变化控制了印度洋沿岸流转向、海平面变化控制了沉积物粒度的变化。此外,在全新世期间,正印度洋偶极子可能导致了由孟加拉湾流向阿拉伯海沿岸流的减弱,而结合气候模拟中全球变暖将导致正印度洋偶极子频发的认识,未来气候变暖的情况下,孟加拉湾低盐水向阿拉伯海的流动可能会受到抑制。因此,预测孟加拉湾与阿拉伯海之间的盐度差异可能越来越大。

Other Abstract

The Indian Coastal current is the main current driving material exchange between the Bay of Bengal and the Arabian Sea. Reconstruction of the past evolutionary history of the Indian Coastal current is essential for predicting future changes in the marine environment of the northern Indian Ocean. However, there are very few studies on its past history and there is almost a gap. This paper presents the clay mineral and grain size record of core MD77-191, located in the sea off southern India, in conjunction with transient climate modelling to trace the history of the Indian Coastal current evolution since the last deglacial. Combined with the published Sr-Nd isotope results, it is concluded that the sediments in core MD77-191 are mainly from a mix of Arabian Sea and Bay of Bengal sediments. The Indian Coastal current is the primary means of sediment transport. During the prevalence of summer monsoon, the Indian Coastal current flows from the Arabian Sea to the Bay of Bengal, and the sediments are mainly of Arabian Sea origin, at which time the smectite/(illite + chlorite) ratios are higher; conversely, during the prevalence of winter monsoon, the Indian Coastal current flows from the Bay of Bengal to the Arabian Sea, and the sediments are mainly of Bay of Bengal origin, with a decrease in the smectite/(illite + chlorite) ratios. Combined with transient climate modelling results, it is inferred that the Indian monsoon shift due to changes in atmospheric circulation patterns in the northern Indian Ocean is the main driving factor. In addition, the grain size and end-member simulation results of core MD77-191 show that the Arabian Sea sediments arriving at station MD77-191 were coarser than the Bay of Bengal sediments during the deglacial from 18 to 9.5 kyr, when winter monsoon was stronger. However, the above phenomenon is reversed from 9.5 ka to the present day, and the Arabian sea sediments are finer than the Bay of Bengal sediments. It is hypothesized that changes in sea level leading to changes in the coarseness and fineness of the sediments of the extensive shelf on the eastern side of the Arabian Sea may be the primary cause, while changes in the Indian summer monsoon influenced by the modal transition of the equatorial Indian Ocean Dipole are a secondary cause.

This paper provides, for the first time, a continuous sedimentary record of material exchange in the northern Indian Ocean marginal sea with a finely defined chronology since the last deglacial. Revealing that large-scale atmospheric circulation changes control the Indian Ocean Coastal current steering, and sea level changes control the changes in sediment grain size. In addition, during the Holocene, the positive Indian Ocean Dipole may have contributed to the weakening of the coastal current from the Bay of Bengal to the Arabian Sea. In conjunction with the realization in climate simulations that global warming will lead to the frequency of the positive Indian Ocean Dipole, the flow of low salinity water from the Bay of Bengal to the Arabian Sea may be suppressed under future warming scenarios. As a result, it is predicted that the salinity difference between the Bay of Bengal and the Arabian Sea may become increasingly large.

Subject Area海洋地质学
MOST Discipline Catalogue理学
Language中文
Table of Contents

1 绪论... 1

1.1 选题背景及研究意义... 1

1.2 印度季风、印度洋偶极子、热带辐合带与边界流之间的关系... 2

1.3 黏土矿物在古环境古气候研究中的应用... 3

1.4 粒度在古环境古气候研究中的应用... 4

1.5 瞬态气候演变模型研究进展... 5

1.6 北印度洋沉积物来源研究进展... 6

1.7 存在问题及选题依据... 8

1.8 研究内容及技术路线图... 9

1.8.1 研究内容... 9

1.8.2 技术路线图及工作量... 10

2 研究材料与方法... 12

2.1 研究区水文及地质背景... 12

2.2 研究材料及年龄模式... 15

2.3 研究方法... 16

2.3.1 样品前处理... 16

2.3.2 黏土矿物测试... 16

2.3.3 粒度测试... 17

2.3.4 瞬态气候演变模型... 17

3 结果... 19

3.1 黏土矿物组成特征... 19

3.2 粒度组成特征... 20

3.3 南亚大陆及北印度洋的海平面气压、表层洋流及表层风分布... 21

4 过去18 kyr大气环流驱动的北印度洋边缘海物质交换... 31

4.1 MD77-191岩芯的黏土矿物来源... 31

4.2 印度沿岸流控制的北印度洋边缘海沉积物交换历史... 33

4.3 大气环流影响的印度洋沿岸流变化... 35

5 过去18 kyr北印度洋边缘海物质交换的粒度记录... 39

5.1 粒度变化的意义... 39

5.2 末次冰消期以来粒度记录指示的印度沿岸流变化历史... 40

5.2.1 海平面变化对粒度组成的影响... 43

5.2.2 印度洋偶极子对粒度组成的影响... 44

5.3 对未来印度沿岸流演化的启示... 45

6 结论与展望... 46

6.1 结论... 46

6.2 展望... 47

参考文献... 48

致谢... 61

作者简历及攻读学位期间发表的学术论文与其他相关学术成果... 63

Document Type学位论文
Identifierhttp://ir.qdio.ac.cn/handle/337002/185167
Collection海洋地质与环境重点实验室
Recommended Citation
GB/T 7714
康晓莹. 末次冰消期以来印度半岛南部岸外沉积历史及其对印度沿岸流演化的指示[D]. 中国科学院海洋研究所. 中国科学院大学,2024.
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