Eddy-Resolving Simulations for the Asian Marginal Seas Using ROMS
Tony Song JPL, California Institute of Technology Tao Tang Hong Kong Baptist University
EQ
10°S
10°N
20°N
30°N
40°N
100°E 120°E 140°E
ASIA
Sea of Japan
South China Sea
East China Sea
Celebes Sea
Flores Sea
PACIFIC
NEC
NECC
MC
KC
Importance:
• Water Exchange
• Indonesian throughflow
• Warm pool & El Nino
Characteristics:
• Complex geometry
• Sleep topography
• Monsoon winds
• Strong currents
Observations: A detached warm eddy from Kuroshio was observed near the Luzon Strait (Li et al. 1998).
warm ring centerAug. 1994
Previous Studies
Fang, G. H. (1995): The structure of the Taiwan-Tsushima-Trugaru Current System and its relation to the Kuroshio. Marine Sciences. 4, 43-48.
Hsueh, Y., J. R. Schults, and W. R. Holland (1997): The Kuroshio flow-through in the East China Sea: A numerical model, Prog. Oceanog. 39, 79-108.
Pohlmann, T. (1987): A three-dimensional circulation model of the South China Sea, in Three-Dimensional Models of Marine and Estuarine Dynamics, edited by J.C.J. Nihoul and B.M. Jamart, pp. 245-268, Elsevier, New York
Metzger, E. J. and H. E. Hurlburt (1996): Coupled dynamics of the South China Sea, the Sulu Sea, and the Pacific Ocean, J. Geophys. Res. 101, 12331-12352.
Model Description
The model uses curvilinear grid with a variable resolution from 10x10 km for the complex geometry of the Asian marginal seas and 30x30 km grid for the eastern Pacific.
Initialized with Levitus T and S; forced by the monthly mean air-sea fluxes of momentum, heat, and freshwater from COADS.
Closed in the north and west, open in the south and east by combining the radiation scheme with nudging technique (Marchesielo et al. 2001)
The challenge is the topographic representation from shallow (e.g. ECS, 60 m) to deep region (Pacific, 5 km) without losing the resolution in the surface layer.
Z = (1+s) + hs + (H-h)c(s), the s-coordinate (Song&Haidvogel 1994)
shallow deep
5000m
10mh
Model Results
Surface layer circulation Deep layer circulation Vertical structure Water exchanges between AMS and Pacific
Kuroshio eddy
Cyclonic circulation
Tsushima Current
Mindanao Current
Strong Kuroshio intrusion
Weak TSWC
cyclones
Deep Western Boundary Current
To SCS
To Selebes
Kuroshio warm rings
Cold and fresh
Upwelling Downwelling
Selebes Sea Luzon Strait
Vertical Structure
Conclusions and Discussion
High-resolution and low-viscosity are key factors for a better representation of the exchange of waters through narrow straits and passages.
The detached eddies near the Luzon Strait play a role in transporting warm and salty water into the SCS, while the cyclonic circulation in the Celebes Sea play a role in contributing cold water to the throughflow.
The WDBC of the Pacific Ocean is found to provide fresher waters to the SCS and the Celebes Sea.
However, it is not clear how much they contribute to the water mass of the SCS water and the throughflow. Future study will focus on model-data comparisons.
Dinner Time