Some indications of a reversed surface flow around Tasmania in the Fine Resolution Antarctic Model (FRAM)

Abstract

[Abstract]: South of Tasmania, the Fine Resolution Antarctic Model (FRAM) shows a narrow band of westward upper layer flow. We argue that this is caused by the closure of the Indonesian passage in FRAM. This is supported by numerical experiments carried out by Hirst & Godfrey (1993). The FRAM surface temperature and salinity distribution exhibits distinct anomalies in the southeast Indian Ocean, in good agreement with anomalies observed in the Hirst & Godfrey (1993) model. Indonesian Throughflow water advects heat into the Indian Ocean; its absence in FRAM results in a lack of thermal energy to warm the Indian Ocean in the model. The surface salinity anomaly is most likely caused by an over-estimated Ekman transport. The weakened heat and salinity transport in FRAM restrict surface convection in the mid-latitude region to approximately 350 m. The effect of the Indonesian Throughflow closure in FRAM is even more dramatic for the circulation around Australia and Tasmania. Hirst & Godfreys (1993) results suggest that in the case of an open Indonesian passage, the flow in the surface layer is eastward, ie from the Indian to the Pacific Ocean. FRAM shows westward flow consistant with a closed Indonesian passage.