ALBERT

Description: Tidal mixing and its associated iron and nutrients flux from a subsurface layer along the shelf break has been considered as one of the key processes to maintain the high summertime biological productivity in the Green Belt in the southeastern Bering Sea. In the present study, tidal mixing near the shelf break is examined with a three-dimensional high-resolution numerical model to quantify the enhanced mixing and to reveal the underlying physical mechanisms based on the different characteristics of diurnal and semi-diurnal internal waves. Strong turbulent mixing with energy dissipation rates of over 1 × 10 -8 W/kg is reproduced along the Green Belt in the numerical model forced by barotropic diurnal and/or semi-diurnal tides at open boundaries. The energy dissipation off the shelf break near the sea surface is enhanced due to the semi-diurnal internal waves, whereas the dissipation near the bottom of the shelf break is enhanced by the diurnal topographically trapped waves. An additional experiment with stratification representative of winter conditions shows a significant influence of stratification on the energy dissipation off the shelf break due to the change in features of both diurnal and semi-diurnal internal waves. Low-mode semi-diurnal baroclinic energy flux from the Aleutian Passes is shown to increase the energy dissipation along the shelf slope between Pribilof and Zhemchug Canyons. These results suggest that the strong vertical mixing along the shelf break induced by the diurnal and semi-diurnal tides both play important roles in maintaining the iron and nutrients supply along the Green Belt.