Enhanced vertical mixing within mesoscale eddies due to high frequency winds in the 2 South China Sea 3 by 4

13 The South China Sea is a marginal basin with a complex circulation influenced by the 14 East Asian Monsoon, river discharge and intricate bathymetry. As a result, both the mesoscale 15 eddy field and the near-inertial energy distribution display large spatial variability and they 16 strongly influence the oceanic transport and mixing. 17 With an ensemble of numerical integrations using a regional ocean model, this work 18 investigates how the temporal resolution of the atmospheric forcing fields modifies the 19 horizontal and vertical velocity patterns and impacts the transport properties in the basin. The 20 response of the mesoscale circulation in the South China Sea is investigated under three different 21 forcing conditions: monthly, daily and six-hourly momentum and heat fluxes. 22 While the horizontal circulation does not display significant differences, the 23 representation of the vertical velocity field displays high sensitivity to the frequency of the wind 24 forcing. If the wind field contains energy at the inertial frequency or higher (daily and six-hourly 25 cases), then Vortex Rossby waves and near inertial waves are excited as ageostrophic expression 26 of the vigorous eddy field. Those waves dominate the vertical velocity field in the mixed layer 27 (vortex Rossby waves) and below the first hundred meters (near inertial waves) and they are 28 responsible for the differences in the vertical transport properties under the various forcing fields 29 as quantified by frequency spectra, vertical velocity profiles and vertical dispersion of 30 Lagrangian tracers. 31 32