| 2009—2017年南沙群岛珊瑚礁砾洲演变 |
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| 引用本文： | 周胜男,施祺,郭华雨,杨红强,严宏强.2009—2017年南沙群岛珊瑚礁砾洲演变[J].热带地理,2020,40(4):694-708. |
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| 作者姓名： | 周胜男 施祺 郭华雨 杨红强 严宏强 |
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| 作者单位： | 1.中国科学院边缘海与大洋地质重点实验室，南海海洋研究所，南海生态环境工程创新研究院，广州 510301;2.南方海洋科学与工程广东省实验室（广州），广州 511458;3.中国科学院南沙海洋生态环境实验站, 三沙 573199;4.中国科学院大学，北京 100049;5.海军后勤部，北京 100841 |
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| 基金项目： | 中国科学院战略性先导科技专项（A类）(XDA13010103);南方海洋科学与工程广东省实验室（广州）人才团队引进重大专项(GML2019ZD0206);中国科学院南海生态环境工程创新研究院创新发展基金项目(ISEE2018PY02) |
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| 摘 要： | 通过对南沙群岛永暑礁、西门礁和安达礁3个砾洲结合现场实测数字高度模型（DEM）的遥感影像分析，重建了2011（2009）、2013、2015、2017年4个时段的砾洲DEM，分析揭示出珊瑚礁砾洲不同时段的地形地貌特征及其演变过程。结果显示：2009—2017年间，安达礁砾洲以侵蚀为主，砾洲不断缩小，平均高度、面积和体积呈下降趋势；2011—2017年间，永暑礁砾洲以水平和垂直加积为主，砾洲不断扩大增高，平均高度、面积和体积呈增长趋势；西门礁砾洲以水平加积为主，面积呈增大趋势，而平均高度呈下降趋势，体积变化趋势不明显。2011—2017年间，永暑礁和西门礁砾洲呈现向东或东南礁坪内侧潟湖方向的移动，而安达礁砾洲2009—2017年间则向西北方向礁坪外侧移动，移动距离明显大于永暑礁和西门礁砾洲。3个砾洲的演变主要受季风浪和台风浪的控制，表现为砾洲缩减向礁坪外侧迁移和砾洲扩展向礁坪内侧潟湖迁移的2种不同演变模式，这与砾洲各自所在礁坪在珊瑚环礁中的位置，以及礁坪形态造成的礁坪水动力环境的差异有关。南沙群岛珊瑚礁砾洲地貌的演变为深入研究南海珊瑚礁灰沙岛地貌发育演化及动力机制提供了重要的科学基础。
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| 关 键 词： | 珊瑚礁 砾洲 数字高度模型（DEM） 多光谱遥感 地貌特征与演变 南沙群岛 |
| 收稿时间： | 2019-10-11 |
Evolution of Coral Shingle Cays in the Nansha Islands during 2009-2017 |
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| Shengnan Zhou,Qi Shi,Huayu Guo,Hongqiang Yang,Hongqiang Yan.Evolution of Coral Shingle Cays in the Nansha Islands during 2009-2017[J].Tropical Geography,2020,40(4):694-708. |
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| Authors: | Shengnan Zhou Qi Shi Huayu Guo Hongqiang Yang Hongqiang Yan |
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| Abstract: | Coral shingle cays are distributed widely around coral reefs and islands in the South China Sea; however, their formation and evolution are little understood. A Digital Elevation Model (DEM) of three coral shingle cays at the Yongshu, Ximen, and Anda reefs, respectively, in the Nasha Islands had been built after they were investigated in 2017. Based on the modern DEMs of the shingle cays, different DEMs of the shingle cays were reconstructed at the past four intervals of 2011 (2009), 2013, 2015 and 2017 by remote sensing analysis; thus, the geomorphic features and evolution that the cays underwent from 2009-2017 was revealed. During this periods, the shingle cay at the Anda Reef experienced near constant erosion, shrinking continuously and showing losses of 50%, 70%, and 72% in average height, area, and volume, respectively, as part of a general declining trend. The shingle cay at the Yongshu Reef was dominated by horizontal and vertical accretions; its average height, area, and volume increased by approximately 21%, 62% and 103%, respectively, from 2011-2017. The area of the shingle cay at the Ximen Reef showed horizontal accretion, with an increase of approximately 160%, but its average height declined by approximately 31% and changes in its volume were insignificant. At both the Yongshu and Ximen reefs, the shingle cays moved eastward or southeastward into the lagoon or inner reef flat, with the centroid being displaced 41.18 m and 55.71 m, respectively; the average rates of movement were 0.6 m/month and 0.8 m/month, respectively. In contrast, the shingle cay at the Anda Reef moved northwestward towards the outer reef flat for a larger distance (193.1 m) and at a greater velocity (2.1 m/month) than the other reefs moved. The evolution of three shingle cays was controlled mainly by monsoon- and typhoon-driven waves, and was influenced by differences in hydrodynamics based on their locations and the shapes of the reef flat. As a result, the three shingle cays showed two different modes of evolution: migration and shrinking towards the outer reef flat and migration and extension into the lagoon or inner reef flat. The geomorphic evolution of these coral shingle cays in the Nansha Islands provides an important scientific basis for extensive study of the geomorphic development, and the dynamic mechanism thereof, of coral islands in the South China Sea. Further research will combine long-term remote sensing analysis and regular field observations of the ecology, sedimentology, and hydrodynamics of the coral shingle cays and neighboring reef areas, and focus on the long-term processes of coral shingle cay formation and evolution to reveal the key environmental factors thereof and the mechanisms affecting them. |
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| Keywords: | coral reef coral shingle cay digital elevation model multispectral remote sensing geomorphic evolution Nansha Islands |
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