黑潮延伸体区跨等密度面湍流混合的次季节变化

海洋中的跨等密度面湍流混合对于热量和淡水输送、翻转环流以及全球气候变化都有重要影响,理解跨等密度面湍流混合的变化对于改进气候模式模拟和预测大尺度海洋环流的能力具有重要作用.基于细尺度参数化方法,本文利用黑潮延伸体区的一个长期潜标K7观测,对跨等密度面湍流混合的次季节变化进行了分析.结果 表明,在2004年6～9月,30...

SUBSEASONAL VARIATION OF TURBULENT DIAPYCNAL MIXING IN THE KUROSHIO EXTENSION REGION

Diapycnal mixing in the ocean affects the heat and freshwater transport, overturning circulation as well as global climate changes. Understanding the variability of diapycnal mixing is important for improving the ability of climate models to simulate and predict the large-scale ocean circulations. Based on a finescale parameterization method, the subseasonal variation of turbulent diapycnal mixing in the Kurshio Extension region was analyzed using measurements of a long-term mooring deployed here. During June to September 2004, the inferred diapycnal mixing exhibits significant month-to-month variation. Within 300~1 350 m, the mean dissipation rate in August is 2.7×10^-9m²/s³, which is about 3 times of the value in September. This significant subseasonal variation of the diapycnal mixing is closely related to that of near-inertial shear variance, which is associated with the wind-induced near-inertial internal waves. In particular, in mid-August, the moderate local wind induces strong near-inertial waves that could reach 1 300 m depth. Energy budget analysis indicates that for the total near-inertial wind work of 1.7×10³W/m² in August, about 71% can radiate into the deep ocean and accounts for 52% of the energy required for diapycnal dissipation. Besides, the deep penetration of near-inertial waves is suggested to be facilitated by the negative geostrophic vorticity at that time. This study provides direct evidence for the important role of wind-induced near-inertial waves in modulating low-frequency variation of diapycnal mixing in deep ocean.