Observation of small-scale processes over shelf break in the East China Sea

Abstract

The turbulent dissipation along with temperature and salinity was measured on board R/V Dong Fang Hong 2 over the shelf break of the East China Sea from March 7 to 9, 2004. Applying the Turner angle, it is found that the ‘diffusive’ double diffusion, salt-fingering, and stable stratification coexist in the upper water column of about 50 m. Below that depth, there exists weak salt-fingering. The turbulent dissipation rates are enhanced along the ray paths of M2 internal tides emanating from the shelf break with values ranging from 1.0×10−1 W·kg−1 to 1.2×10−6 W·kg−1. The corresponding diapycnal mixing rates are from 1×10−6 m2·s−1 to l×10−2 m2·s−1. The spatially averaged mixing rate over the whole observation section is 2.3×10−3 m2·s−1, which is much larger than 1×10−5 m2·s−1 of the background diapycnal mixing rate in the open ocean.