On the Indonesian Throughflow in the OCCAM 1/4 degree ocean model

[摘要] The Indonesian Throughflow is analysed in two runs of the OCCAM 1/4 degreeglobal ocean model, one using monthly climatological winds and one usingECMWF analysed six-hourly winds for the period 1993 to 1998. The long-termmodel throughflow agrees with observations and the value predicted byGodfrey's Island Rule. The Island Rule has some skill in predicting theannual signal each year but is poor at predicting year to year and shorterterm variations in the total flow, especially in El Niño years.

The spectra of transports in individual passages show significant differencesbetween those connecting the region to the Pacific Ocean and those connectingwith the Indian Ocean. On investigation we found that changes in the northerntransports were strongly correlated with changes in the position of currentsin the Celebes Sea and off Halmahera. Vertical profiles of transport are inreasonable agreement with observations but the model overestimates the nearsurface transport through the Lombok Strait and the dense overflow from thePacific through the Lifamatola Strait into the deep Banda Sea. In both casesthe crude representation of the passages by the model appears responsible.

In the north the model shows, as expected, that the largest transport is viathe Makassar Strait. However this is less than expected and instead there issignificant flow via the Halmahera Sea. If Godfrey's Island Rule is correctand the throughflow is forced by the northward flow between Australia andSouth America, then the Halmahers Sea route should be important. It is themost southerly route around New Guinea to the Indian Ocean and there is noapparent reason why the flow should go further north in order to pass throughthe Makassar Strait. The model result thus raises the question of why inreality the Makassar Strait route appears to dominate the throughflow.

[学科分类] 海洋学与技术