The long-term variations of density structure and hypoxia were examined numerically with a quasi three-dimensional numerical ocean model in order to elucidate the dynamic process of hypoxia in Mikawa Bay. The numerical results revealed that the bottom water was isolated by density stratification due to the increase in temperature and river inflow in summer season and the dissolved oxygen in the isolated bottom water was consumed, resulting in the formation of hypoxia. Moreover, the MODIS SST and the observation data were assimilated into the numerical simulation by the nudging method to furthermore improve the computation accuracy. The validity of data assimilation in Ise Bay area was confirmed from the comparison of the numerical results and the observation data.
