利用高分辨率水体反射地震资料研究吕宋海峡以东黑潮区混合

Study on Kuroshio mixing located in the east of Luzon Strait by using high-resolution seawater seismic reflection data

混合过程是海洋中普遍存在的一种形式,对气候变化、物质分布等起到了重要作用。地震海洋学是近十多年发展起来的一门新兴学科,被广泛应用到物理海洋学问题的研究中,具有高空间分辨率的突出优点。文章利用反射地震资料,通过斜率谱方法,分别获得了吕宋海峡以东黑潮区湍流段与内波段的耗散率及扩散率。结果显示,在剖面深度200~800m的平均耗散率为10^-7.0W·kg^-1,平均扩散率为10^-3.3m^2·s^-1,比大洋统计均值10^-5.0m^2·s^-1高约1~2个量级,与前人在吕宋海峡的观测结果相一致。湍流段和内波段的扩散率空间分布差异较大:湍流段扩散率高值区对应强流区域,推测这里是中尺度涡边缘,其次中尺度不稳定过程引起扰动增强,进而引起湍流混合的加强;内波段扩散率高值区出现在吕宋岛弧附近,推测是内波遇到岛弧地形发生破碎,进而引起强的内波混合。

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^-7.0 W·kg^-1,and the average diffusivity is 10^-3.3 m^2·s^-1,which is about 1-2 order of magnitude higher than the average value in the ocean 10^-5.0 m^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.