Title: The influence of explicit tidal forcing in a climate ocean circulation model

Journal: Acta Oceanologica Sinica, 35(9): 42-50

Authors: YU Y., H. Liu* and J. Lan

Abstract:The eight main tidal constituents have been implemented in the global ocean general circulation model with approximate 1° horizontal resolution. Compared with the observation data, the patterns of the tidal amplitudes and phases had been simulated fairly well. The responses of mean circulation, temperature and salinity are further investigated in the global sense. When implementing the tidal forcing, wind-driven circulations are reduced, especially those in coastal regions. It is also found that the upper cell transport of the Atlantic meridional overturning circulation (AMOC) reduces significantly, while its deep cell transport is slightly enhanced from 9×10⁶ m³/s to 10×10⁶ m³/s. The changes of circulations are all related to the increase of a bottom friction and a vertical viscosity due to the tidal forcing. The temperature and salinity of the model are also significantly affected by the tidal forcing through the enhanced bottom friction, mixing and the changes in mean circulation. The largest changes occur in the coastal regions, where the water is cooled and freshened. In the open ocean, the changes are divided into three layers: cooled and freshened on the surface and below 3 000 m, and warmed and salted in the middle in the open ocean. In the upper two layers, the changes are mainly caused by the enhanced mixing, as warm and salty water sinks and cold and fresh water rises; whereas in the deep layer, the enhancement of the deep overturning circulation accounts for the cold and fresh changes in the deep ocean.