Energetics of semidiurnal internal tides near Madagascar in the Southwest Indian Ocean

Abstract

The semi-diurnal internal tidal energetics near Madagascar Island in the Southwest Indian Ocean were analyzed based on a numerical simulation. The baroclinic energy budget revealed that internal tides radiating from the north of Madagascar Island (NMI) and the south of Madagascar Island (SMI), especially those from the continental slope, were the dominant energy sources of the baroclinic energy dissipation in the deep ocean of surrounding areas. In NMI and SMI, the most intense baroclinic energy dissipation and internal tide-induced diapycnal mixing occurred near ridges and seamounts, with depth-integrated energy dissipation of O(10-1-100) W·m−2, dissipation rates of O(10-7-10-6) W·kg−1 and diapycnal diffusivity of O(10-3-10-2) m2·s−1, about one order of magnitude larger than those in most areas of the Mozambique Channel near the 200-m isobath. These estimates based on the numerical simulation were comparable with previous results based on microstructure measurements or fine-scale parameterizations, and suggested that the remotely generated internal tides played an important role in the baroclinic energy dissipation in the deep ocean.