Journal of Tropical Oceanography >
Study on Kuroshio mixing located in the east of Luzon Strait by using high- resolution seawater seismic reflection data
Copy editor: SUN Shu-jie
Received date: 2018-11-04
Request revised date: 2019-01-17
Online published: 2019-07-21
Supported by
National Natural Science Foundation of China((41776040、41830538、41576070);)
Foundation of State Key Laboratory of Tropical Oceanography((LTOZZ1701).)
Copyright
Mixing is a ubiquitous motion in the ocean, which plays an important role in climate change and matter distribution. Seismic Oceanography is a new discipline in recent 10 years; it has been widely applied to Physical Oceanography, because it has the advantage of high spatial resolution. Seismic reflection data were used in this study, along with slope spectral method. We obtained the dissipation rate and diffusivity of turbulence interval and internal wave interval respectively in the Kuroshio (located in the east of the Luzon Strait). The results show that the average dissipation rate from 200- to 800-m depth in this profile is 10 -7.0W·kg -1, and the average diffusivity is 10 -3.3m 2·s -1, which is about 1-2 order of magnitude higher than the average value in the ocean 10 -5.0m 2·s -1. This result is consistent with previous mixing observations in the Luzon Strait. There is a big difference in diffusivity spatial distribution between turbulence interval and internal wave interval: the region where strong current occurs is consistent with that of high turbulence diffusivity in the profile, from which we can infer that this place may be the periphery of mesoscale eddy; its sub-mesoscale instability can strengthen the destabilization and then lead to strong mixing. The high internal wave diffusivity appears near the Luzon Arc, which indicates that the internal wave breaking occurs when it meets the island arc, leading to strong internal wave mixing.
Key words: Kuroshio; seismic reflection; slope spectra; mixing
ZHANG Zhe , JING Zhiyou , TANG Qunshu . Study on Kuroshio mixing located in the east of Luzon Strait by using high- resolution seawater seismic reflection data[J]. Journal of Tropical Oceanography, 2019 , 38(4) : 20 -29 . DOI: 10.11978/2018113
图1 2001年8月6日航次测线周围海域水深地形(a)和SLA(海表面高度异常)(b)黑色线段表示完整的航次测线, 红色线段表示本文研究使用的部分测线, 箭头表示由SLA计算得到的地转流 Fig. 1 Bathymetry of the region around the survey line (a) and SLA (b) during the cruise on 6th August 2001. The black line indicates the whole seismic transect during the cruise, the red line indicates the part of the transect used in this study, and the black arrows indicate the geostrophic current calculated by SLA |
图3 浮力频率随深度的变化曲线竖直红线表示参考浮力频率值(3.0cph), 竖直绿线表示研究区域浮力频率均值(3.9cph), cph为周频率cycles per hour的缩写,1cph=(1/3600)s Fig. 3 Buoyancy frequency curve varying with depth. The vertical red line indicates the reference buoyancy frequency (3.0cph), and the vertical green line indicates the average buoyancy frequency (3.9cph) in the study region, cph is the abbreviation of cycles per hour, 1cph=(1/3600)s |
图4 水平斜率谱的平均共使用916条水平斜率谱计算谱的平均, 误差棒表示95%置信区间; 竖直虚线内为内波段区间, 竖直实线内为湍流段区间; 两条倾斜线段斜率为1/3和-1/2, 分别用来拟合湍流段和内波段的斜率谱 Fig. 4 The average horizontal slope spectra. A total of 916 slope spectra are used to calculate average slope spectra, and error bars represent 95% bootstrap confidence interval. The internal wave interval is within the two vertical dashed lines, and the turbulence interval is within the two vertical solid lines. The slopes of two tilted lines are 1/3 and -1/2, respectively, which are used for fitting the slope spectra of turbulence and internal wave intervals |
图5 两条典型的水平斜率谱误差棒表示95%置信区间, 竖直虚线和竖直实线的含义同 Fig. 5 Two typical slope spectra. Error bars represent 95% bootstrap confidence intervals. The meaning of vertical dashed lines and vertical solid lines are explained in |
图6 湍流段计算得到的耗散率(a)和扩散率(b)图中虚线方框内为混合强烈区域 Fig. 6 Calculated dissipation rate (a) and diffusivity (b) by turbulence interval. The rectangle marks the strong mixing area |
[1] |
拜阳, 宋海斌, 董崇志 , 等, 2015. 地震海洋学方法在海洋混合参数提取中的研究与应用——以南海内波和地中海涡旋为例[J]. 地球物理学报, 58(7):2473-2485.
|
[2] |
范植松 , 2002. 海洋内部混合研究基础[M]. 北京: 海洋出版社.
|
[3] |
冯士筰, 李凤岐, 李少菁 , 1999. 海洋科学导论[M]. 北京: 高等教育出版社.
|
[4] |
宋海斌, 董崇志, 陈林 , 等, 2008. 用反射地震方法研究物理海洋—地震海洋学简介[J]. 地球物理学进展, 23(4):1156-1164.
|
[5] |
郑瑞玺, 经志友, 罗士浩 , 2018. 南海北部反气旋涡旋边缘的次中尺度动力过程分析[J]. 热带海洋学报, 37(3):19-25.
|
[6] |
|
[7] |
|
[8] |
|
[9] |
|
[10] |
|
[11] |
|
[12] |
|
[13] |
|
[14] |
|
[15] |
|
[16] |
|
[17] |
|
[18] |
|
[19] |
|
[20] |
|
[21] |
|
[22] |
|
[23] |
|
[24] |
|
[25] |
|
[26] |
|
[27] |
|
[28] |
|
[29] |
|
[30] |
|
[31] |
|
[32] |
|
[33] |
|
[34] |
|
[35] |
|
[36] |
|
[37] |
|
[38] |
|
[39] |
|
[40] |
|
[41] |
|
[42] |
|
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