Submesoscale turbulence is important in closing oceanic energy pathway from forcing to dissipative scales. Based on in situ underway velocity and hydrographic measurements throughout the four seasons, this study investigates the seasonality of submesoscale turbulence in the upper northern South China Sea. In spring and summer, the spectral slope of potential energy spectra within 1–10 km is close to k-3, consistent with interior quasigeostrophic dynamics, while it is close to k-2 in autumn and winter, suggestive of enhanced impacts of ageostrophic submesoscale dynamics. Density wavenumber spectra for an anticyclonic eddy show a steeper spectral slope at eddy periphery than that at eddy center, opposite to previous observations and theoretical expectation. High-resolution sea-surface-temperature images imply that the discrepancy is probably due to the fact that transects selected at eddy center have experienced stronger temperature gradients than those at eddy peripheries.
In addition, this talk will also cover preliminary results from a recent cruise (May 2017) that was dedicated to study submesoscale, cross-frontal, processes in the Taiwan Strait. The observations were designed to be submesoscale-resolving (~2 km resolution) in the frontal region.