Wang, Shouyi, Ummenhofer, Caroline C., Oppo, Delia W., Murty, Sujata A., Wagner, Patrick , Böning, Claus W. and Biastoch, Arne (2023) Freshwater Contributions to Decadal Variability of the Indonesian Throughflow. Geophysical Research Letters, 50 (14). Art.Nr. e2023GL103906. DOI 10.1029/2023GL103906.

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Abstract

The Makassar Strait, the main passageway of the Indonesian Throughflow (ITF), is an important component of Indo-Pacific climate through its inter-basin redistribution of heat and freshwater. Observational studies suggest that wind-driven freshwater advection from the marginal seas into the Makassar Strait modulates the strait's surface transport. However, direct observations are too short (<15 years) to resolve variability on decadal timescales. Here we use a series of global ocean simulations to assess the advected freshwater contributions to ITF transport across a range of timescales. The simulated seasonal and interannual freshwater dynamics are consistent with previous studies. On decadal timescales, we find that wind-driven advection of South China Sea (SCS) waters into the Makassar Strait modulates upper-ocean ITF transport. Atmospheric circulation changes associated with Pacific decadal variability appear to drive this mechanism via Pacific lower-latitude western boundary current interactions that affect the SCS circulation.

Key Points:
- A global ocean model is used to show how freshwater impacts the decadal variability of transport through the main Indonesian Throughflow pathway
- Wind-driven advection of South China Sea freshwater induces an upstream pressure gradient that reduces transport
- Freshwater input is modulated by atmospheric circulation changes associated with Pacific decadal variability

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