A numerical simulation of the Indonesaian Throughflow with a Mixed Layer-Isopycnal Ocean General Circulation Model.
by
S. Nakamoto1,2 J. Oberhuber 3
K. Ueyoshi4, W. White 4,
J. She 5 and K. Muneyama 2
1. Earth Science and Technology Organization,
Roppongi-First Bldg, 1-9-9 Roppongi, Minatoku, Tokyo 106
2. Japan Marin Science and Technology Center,
Yokosuka, Kanagawa, 237, Japan
3. German Climate Computer Center
Hamburg, Germany
4. Scripps Institution of Oceanography,
University of California at San Diego
La Jolla, CA
5. First Institute of Oceanography,
State Oceanographic Administration,
Qingdao, China
Abstract
An ocean general circulation model (OGCM) formulated on isopycnal coordinates is used to model the flow through Pacific Ocean to Indian Ocean (Indonesian Througflow). The model domain is global ocean with isopycnals as Lagrangian coordinates in the vertical and predicts a free surface. Prognostic fields of temperature and salinity enter the dynamics as active tracers through a realistic equation of state. The surface boundary layer is parameterized by a detailed mixed-layer model.
Initial conditions are observed annual mean temperature and salinity. Monthly heat fluxes and wind stresses are used to force the ocean model. After adjustment period the ocean approaches a cyclo-stationary state, except for the deep ocean where temperature and salinity have not become stationary.
The model temperature at 500m and 1000m exhibits annual cycle, indicating the wind stress-and heat flux forcing from the sea surface. Velocity anomaly at these depths also shows annual cycle and indicates northward flow from the Indian Ocean to the Pacific Ocean. The flow through Indonesian seas in the mixed layer and the second layer (whose bottom is situated at 175m) are fairly similar to those arising in other models (the maximum volume transport of 12 Sv in summer and the minimum of 2 Sv in winter.) In summer the Mindanao current takes the west paths ( from the Celebes sea through Floles sea into the Indian Ocean ) and penetrates down to 1400m depth at 2S. At l0S northward flow from the Indian Ocean is dominant between 800m and 2100m, while the southward flow from surface to 800m in the western half and from the surface to 300m in the eastern half of Banda strait are traced back to the Pacific Ocean. The vertically integrated total volume transport showed maximum southward transport of 23 Sv in February and minimum southward transport of 12 Sv in June, with annual averaged southward total transport being 17 Sv.
