A Numerical Study Of The Influence Of The Global Ocean On The Variabilities Of The Southeast Asian Marginal Seas Circulation

A variable-grid global ocean circulation model was established to study thevariabilities of the Southeast Asian marginal seas circulation. The model was basedon GFDL's MOM2 with fine grid (1°/6) covering the area from 20°S to 60°N andfrom 98°E to 156°E and coarse grid (2°) in the rest part of the world ocean. On thebasis of well simulating the seasonal variation of the Southeast Asian marginal seascirculation, the model simulated the interannual variation of the circulation from 1994to 2000. The computation shows that the upper layer circulation of the South ChinaSea has obvious interannual variabilities. During summer of the El Ni?o year thevariation is not remarkable. During summer of the L Ni?a year both the southernanti-cyclonic and the northern cyclonic gyres are weakened. During winter of the ElNi?o year the cyclonic gyre is weakened. During winter of the L Ni?a year thecyclonic gyre is enhanced. In August of 1998, the upper layer circulation remarkablydiffered from the normal years. The southern anti-cyclonic gyre vanished and thenorthern cyclonic gyre was replaced by an anti-cyclonic circulation. The off-shorecurrent southeast of Vietnam vanished, resulting in intensification of the warm eventof 1998. The mass transport through Taiwan- Iriomote Passage has obviousinterannual variabilities with smaller transport during El Ni?o and larger transportduring L Ni?a. The interannual variation of upper 35m transport through the LuzonStrait was closely related with the zonal wind stress variabilities over the Luzon Strait,while the mass transport between 35-427m through Luzon Strait was closely relatedwith the interannual variation of mass transport through Taiwan- Iriomote Passage.The correlationcoefficient between the averaged temperature of the upper 58m of theSouth China Sea and the wind stress of the South China Sea is –0.86, indicating the IIinterannual variability of upper layer temperature was affected by the wind stressvariability The interannual variation of averaged temperature between 58-209m is outof phase in relation with the upper layer. It is affected by the interannual variability ofthe vertical velocity through the subsurface layer. The annual mean mass transportrelated to 800m through IX1 section is 11.6Sv, with greater values in summer andsmaller values in winter. Semi-annual variability of mass transport is apparent in theLombok Strait and Ombai Strait, but does not extend to the Timor Sea. The masstransport of the Timor Sea has apparent annual variability while both semi-annual andannual variability are apparent in the Ombai Strait. These variabilities are associatedwith the variability in the extension area of the eastward South Java Current duringtwo monsoon transition periods. The interannual variation of mass transport throughIX1 section relative to 800m has a good relationship with ENSO. The correlationcoefficient with the Ni?o3 index is –0.75 indicating smaller transport during El Ni?oand larger transport during L Ni?a.