{"title":"内波对西沙群岛海底热结构和湍流混合的影响","authors":"Ming-Quan Zhu , Xian-Rong Cen , Sheng-Qi Zhou , Yuan-Zheng Lu , Shuang-Xi Guo , Peng-Qi Huang , Ling Qu","doi":"10.1016/j.dsr.2024.104327","DOIUrl":null,"url":null,"abstract":"<div><p>Using velocity and high-resolution temperature mooring data from the fore-reef slope of Yongxing Island in the northwest South China Sea (water depth of 69 m), we examine the effects of internal waves on the temporal variations in temperature, bottom mixed layer (BML) and turbulent mixing. The diurnal tide is found to be the dominant tidal force and the baroclinic tide is highly active, which would account for the 11 d abnormal spring-neap cycle in the barotropic tidal current. During the ebb period (tidal elevation decreases), the bottom diurnal baroclinic current transports cold water upslope, resulting in a decrease in temperature, and vice versa during the flood period. The BML thickness <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> widely varies around <span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>m</mi></mrow></math></span>, approximately 2% of the water depth. The bottom turbulent mixing is not so active, indicated by the bulk dissipation <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> of 10 <span><math><mrow><mi>mW</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></mrow></math></span> and turbulent diffusivity <span><math><msub><mrow><mi>κ</mi></mrow><mrow><mi>z</mi></mrow></msub></math></span> of <span><math><mrow><mn>2</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math></span> <span><math><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. Both <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> approximate a log-normal distribution, demonstrating strong intermittency. The high-frequency <span><math><mrow><mo>(</mo><mi>ω</mi><mo>)</mo></mrow></math></span> internal bores can increase <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> by four times and enhance the turbulent mixing by one order, which should be responsible for the slow cascade of <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> <span><math><mrow><mo>(</mo><mo>∼</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>5</mn></mrow></msup><mo>)</mo></mrow></math></span> and <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> <span><math><mrow><mo>(</mo><mo>∼</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></msup><mo>)</mo></mrow></math></span>. In the downslope phase, <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> is about 30% thicker, and turbulent mixing is enhanced by 3 times stronger than those in the upslope phase. It is revealed that under the forcing of internal waves, turbulent mixing corresponds to a thick BML with <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub><mo>∼</mo><msup><mrow><mrow><mo>〈</mo><msub><mrow><mi>κ</mi></mrow><mrow><mi>z</mi></mrow></msub><mo>〉</mo></mrow></mrow><mrow><mn>0</mn><mo>.</mo><mn>25</mn></mrow></msup></mrow></math></span>, and stratification (<span><math><mi>N</mi></math></span>) has a significantly negative correlation with the development of BML, <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub><mo>∼</mo><msup><mrow><mrow><mo>〈</mo><mi>N</mi><mo>〉</mo></mrow></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>8</mn></mrow></msup></mrow></math></span>.</p></div>","PeriodicalId":51009,"journal":{"name":"Deep-Sea Research Part I-Oceanographic Research Papers","volume":"209 ","pages":"Article 104327"},"PeriodicalIF":2.3000,"publicationDate":"2024-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Effects of internal waves on bottom thermal structures and turbulent mixing in the Xisha Islands\",\"authors\":\"Ming-Quan Zhu , Xian-Rong Cen , Sheng-Qi Zhou , Yuan-Zheng Lu , Shuang-Xi Guo , Peng-Qi Huang , Ling Qu\",\"doi\":\"10.1016/j.dsr.2024.104327\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>Using velocity and high-resolution temperature mooring data from the fore-reef slope of Yongxing Island in the northwest South China Sea (water depth of 69 m), we examine the effects of internal waves on the temporal variations in temperature, bottom mixed layer (BML) and turbulent mixing. The diurnal tide is found to be the dominant tidal force and the baroclinic tide is highly active, which would account for the 11 d abnormal spring-neap cycle in the barotropic tidal current. During the ebb period (tidal elevation decreases), the bottom diurnal baroclinic current transports cold water upslope, resulting in a decrease in temperature, and vice versa during the flood period. The BML thickness <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> widely varies around <span><math><mrow><mn>1</mn><mo>.</mo><mn>5</mn><mspace></mspace><mi>m</mi></mrow></math></span>, approximately 2% of the water depth. The bottom turbulent mixing is not so active, indicated by the bulk dissipation <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> of 10 <span><math><mrow><mi>mW</mi><mspace></mspace><msup><mrow><mi>m</mi></mrow><mrow><mo>−</mo><mn>2</mn></mrow></msup></mrow></math></span> and turbulent diffusivity <span><math><msub><mrow><mi>κ</mi></mrow><mrow><mi>z</mi></mrow></msub></math></span> of <span><math><mrow><mn>2</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mo>−</mo><mn>4</mn></mrow></msup></mrow></math></span> <span><math><mrow><msup><mrow><mi>m</mi></mrow><mrow><mn>2</mn></mrow></msup><mspace></mspace><msup><mrow><mi>s</mi></mrow><mrow><mo>−</mo><mn>1</mn></mrow></msup></mrow></math></span>. Both <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> and <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> approximate a log-normal distribution, demonstrating strong intermittency. The high-frequency <span><math><mrow><mo>(</mo><mi>ω</mi><mo>)</mo></mrow></math></span> internal bores can increase <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> by four times and enhance the turbulent mixing by one order, which should be responsible for the slow cascade of <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> <span><math><mrow><mo>(</mo><mo>∼</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>5</mn></mrow></msup><mo>)</mo></mrow></math></span> and <span><math><msub><mrow><mi>E</mi></mrow><mrow><mi>ɛ</mi></mrow></msub></math></span> <span><math><mrow><mo>(</mo><mo>∼</mo><msup><mrow><mi>ω</mi></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>0</mn></mrow></msup><mo>)</mo></mrow></math></span>. In the downslope phase, <span><math><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub></math></span> is about 30% thicker, and turbulent mixing is enhanced by 3 times stronger than those in the upslope phase. It is revealed that under the forcing of internal waves, turbulent mixing corresponds to a thick BML with <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub><mo>∼</mo><msup><mrow><mrow><mo>〈</mo><msub><mrow><mi>κ</mi></mrow><mrow><mi>z</mi></mrow></msub><mo>〉</mo></mrow></mrow><mrow><mn>0</mn><mo>.</mo><mn>25</mn></mrow></msup></mrow></math></span>, and stratification (<span><math><mi>N</mi></math></span>) has a significantly negative correlation with the development of BML, <span><math><mrow><msub><mrow><mi>H</mi></mrow><mrow><mi>b</mi><mi>m</mi><mi>l</mi></mrow></msub><mo>∼</mo><msup><mrow><mrow><mo>〈</mo><mi>N</mi><mo>〉</mo></mrow></mrow><mrow><mo>−</mo><mn>1</mn><mo>.</mo><mn>8</mn></mrow></msup></mrow></math></span>.</p></div>\",\"PeriodicalId\":51009,\"journal\":{\"name\":\"Deep-Sea Research Part I-Oceanographic Research Papers\",\"volume\":\"209 \",\"pages\":\"Article 104327\"},\"PeriodicalIF\":2.3000,\"publicationDate\":\"2024-07-01\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Deep-Sea Research Part I-Oceanographic Research Papers\",\"FirstCategoryId\":\"89\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S0967063724000979\",\"RegionNum\":3,\"RegionCategory\":\"地球科学\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"OCEANOGRAPHY\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Deep-Sea Research Part I-Oceanographic Research Papers","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0967063724000979","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"OCEANOGRAPHY","Score":null,"Total":0}
Effects of internal waves on bottom thermal structures and turbulent mixing in the Xisha Islands
Using velocity and high-resolution temperature mooring data from the fore-reef slope of Yongxing Island in the northwest South China Sea (water depth of 69 m), we examine the effects of internal waves on the temporal variations in temperature, bottom mixed layer (BML) and turbulent mixing. The diurnal tide is found to be the dominant tidal force and the baroclinic tide is highly active, which would account for the 11 d abnormal spring-neap cycle in the barotropic tidal current. During the ebb period (tidal elevation decreases), the bottom diurnal baroclinic current transports cold water upslope, resulting in a decrease in temperature, and vice versa during the flood period. The BML thickness widely varies around , approximately 2% of the water depth. The bottom turbulent mixing is not so active, indicated by the bulk dissipation of 10 and turbulent diffusivity of . Both and approximate a log-normal distribution, demonstrating strong intermittency. The high-frequency internal bores can increase by four times and enhance the turbulent mixing by one order, which should be responsible for the slow cascade of and . In the downslope phase, is about 30% thicker, and turbulent mixing is enhanced by 3 times stronger than those in the upslope phase. It is revealed that under the forcing of internal waves, turbulent mixing corresponds to a thick BML with , and stratification () has a significantly negative correlation with the development of BML, .
期刊介绍:
Deep-Sea Research Part I: Oceanographic Research Papers is devoted to the publication of the results of original scientific research, including theoretical work of evident oceanographic applicability; and the solution of instrumental or methodological problems with evidence of successful use. The journal is distinguished by its interdisciplinary nature and its breadth, covering the geological, physical, chemical and biological aspects of the ocean and its boundaries with the sea floor and the atmosphere. In addition to regular "Research Papers" and "Instruments and Methods" papers, briefer communications may be published as "Notes". Supplemental matter, such as extensive data tables or graphs and multimedia content, may be published as electronic appendices.