| 引用本文: | 康晓莹,于兆杰,Christophe Colin,万世明.2026.末次冰消期以来粒度记录的北印度洋边缘海物质交换历史[J].地球环境学报,17(3):711-723 |
| KANG Xiaoying,YU Zhaojie,COLIN Christophe,WAN Shiming.2026.Material exchange history of the North Indian Ocean marginal seas recorded by grain size since the last deglaciation[J].Journal of Earth Environment,17(3):711-723 |
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| 末次冰消期以来粒度记录的北印度洋边缘海物质交换历史 |
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康晓莹1，2，于兆杰1，3，Christophe Colin4，万世明1
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1.中国科学院海洋研究所 中国科学院海洋地质与环境重点实验室, 青岛 266071 ；2.中国科学院大学, 北京 100049 ；3.山东科技大学 地球科学与工程学院, 青岛 266590 ；4. Faculty of Earth Sciences, Université Paris-Saclay, Paris 91405, France
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| 摘要: |
| 印度沿岸流是孟加拉湾和阿拉伯海物质交换的主要通道, 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。通过印度半岛以南海域MD77-191岩芯的粒度和端元模拟分析, 结合已发表的锶-钕(Sr-Nd)同位素结果, 发现夏季风盛行时, 沉积物主要为阿拉伯海源; 冬季风盛行时, 主要为孟加拉湾源。将端元组分含量变化与气候指标对比发现: 18.0—9.5 ka, 阿拉伯海源沉积物较孟加拉湾源更粗; 9.5 ka至今, 反向变化。推测海平面变化是导致以上现象的主要原因, 而印度洋偶极子(IOD)相位变化是次要原因。文章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。根据全球变暖将导致IOD频发的推论, 未来孟加拉湾低盐水向阿拉伯海的流动可能会受到抑制, 两个边缘海的盐度差异可能越来越大。 |
| 关键词: 粒度 端元分析 印度季风 印度洋偶极子 北印度洋 海平面变化 |
| DOI：10.7515/JEE2024046 |
| CSTR：32259.14.JEE2024046 |
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| Material exchange history of the North Indian Ocean marginal seas recorded by grain size since the last deglaciation |
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KANG Xiaoying1，2，YU Zhaojie1，3，COLIN Christophe4，WAN Shiming1
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1. Key Laboratory of Marine Geology and Environment, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071 , China ；2. University of Chinese Academy of Sciences, Beijing 100049 , China ；3. School of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao 266590 , China ；4. Faculty of Earth Sciences, Université Paris-Saclay, Paris 91405, France
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| Abstract: |
| Background, aim, and scope The Bay of Bengal and the Arabian Sea are two marginal seas in the northern Indian Ocean with distinct physicochemical properties. Due to the isolation by the South Asian continent, material exchange between them occurs primarily through the Indian coastal current. Reconstructing the evolutionary history of the Indian coastal current and understanding its variability are crucial for predicting future marine environmental changes in the northern Indian Ocean. However, reliable reconstruction records of this coastal current have not yet been published. This study aims to reconstruct the evolutionary history of the Indian coastal current and the material exchange between the Bay of Bengal and the Arabian Sea. Materials and methods This study is based on sediment core MD77-191(7°30′N, 76°43′E), collected from the southern margin of the Indian subcontinent. A total of 369 sediment samples, covering 854 cm of the core and spanning the interval from 0.5 ka to 18.0 ka, were obtained for analysis. Grain size compositions of terrigenous clastic sediments were analyzed, and an end-member modeling algorithm was applied to isolate the dominant grain size end-members. Sediment provenance was constrained using previously published Sr-Nd isotopic data obtained from the same core. By further comparing these results with other climatic proxies, we reconstructed the history of sediment provenance shifts and their implications for changes in coastal current direction. Results The results indicate that the mixing of two end members can explain approximately 90% of the grain size variation in core MD77-191. The modal grain sizes of end-members EM1 and EM2 are 8 μm and 16 μm, respectively. Combined with published Sr-Nd isotope data, it was found that during the prevailing summer monsoon, sediments primarily originate from the Arabian Sea, while during the prevailing winter monsoon, they mainly derive from the Bay of Bengal. During 18.0—9.5 ka, the finer end-member EM1 content was higher during the cold periods of the Younger Dryas (YD) and Heinrich Stadial 1 (HS1) when the summer monsoon was weaker. In contrast, EM1 content decreased during the warmer Bølling-Allerød (B/A) and Early Holocene periods when the summer monsoon was stronger. Since 9.5 ka, EM1 content was higher during the warm Mid-Holocene with a stronger summer monsoon and lower during the cold Late Holocene with a weaker summer monsoon. This indicates that sediments from the Arabian Sea were coarser than those from the Bay of Bengal from 18.0 ka to 9.5 ka, but this trend reversed after 9.5 ka. Discussion This phenomenon may be attributed to the broader continental shelf on the western side of the Indian Peninsula (eastern Arabian Sea). During the low sea level period of 18.0—9.5 ka, the continental shelf was exposed, and river mouths extended seaward. This allowed the summer monsoon-driven West Indian coastal current (WICC) to transport coarser sediments from the Arabian Sea more readily. In contrast, the narrower continental shelf on the eastern side of the Indian Peninsula (western Bay of Bengal) was less affected by sea level changes in terms of river mouth positions. Additionally, the southward flow of the East Indian coastal current (EICC) was obstructed and slowed by Sri Lanka. This caused coarser sediments from the Bay of Bengal to be deposited more readily during transport, resulting in relatively finer sediments reaching the core site. During high sea level periods, the grain size of sediments from the Bay of Bengal did not change significantly. However, the western continental shelf was submerged, and river mouths retreated. Combined with enhanced sediment weathering and erosion due to higher temperatures and increased precipitation during the Holocene, sediments from the Arabian Sea became finer overall. Furthermore, during the low sea level period of 18.0—9.5 ka, the positive Indian Ocean dipole (IOD) enhanced the summer monsoon. This promoted the WICC to transport more coarse sediments from the Arabian Sea, while finer sediments from the Bay of Bengal dominated during weaker summer monsoon periods. During the negative IOD phase since 9.5 ka, sediments from the Bay of Bengal increased, and coarser sediments from the Arabian Sea were blocked from reaching the core site. Conclusions In conclusion, sea level changes are the primary controlling factor for grain size variations in the core, while phase changes in the IOD act as a secondary factor. Recommendations and perspectives Based on the hypothesis that global warming may lead to more frequent positive IOD phase, it is expected that the transport of low-salinity water from the Bay of Bengal to the Arabian Sea may be suppressed in the future. This could further widen the salinity differences between the two marginal seas. |
| Key words: grain size end member analysis Indian monsoon Indian Ocean dipole North Indian Ocean sea level change |
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