Unprecedented response of Indonesian throughflow to anomalous Indo-Pacific climatic forcing in 2016

The Indonesian throughflow (ITF) transport in the upper layer of Makassar Strait was unprecedentedly reduced by 40% during June - September 2016, the weakest boreal summer ITF transport measured through 2004 - mid 2017. A strong negative Indian Ocean Dipole (IOD) event occurring through boreal summer and fall 2016 is the main driver for the reduced ITF transport. Elevated sea surface temperature and height off the southern coast of Java island, attributed to the IOD event, suppressed the Pacific to Indian pressure gradient, resulting in a reduction in the ITF transport. Intensified Wyrtki jets along the equator, energetic westerly winds (including those attributed to the Madden-Julian Oscillations) and downwelling Kelvin waves off Java associated with the strong IOD contributed to the suppressed Indo-Pacific pressure gradient. El Niño-Southern Oscillation did not directly control the anomalous ITF transport but set up conditions favorable for the initiation of the IOD event. This study showcases the role of coupled ocean-atmosphere interactions in Indian Ocean in regulating an extreme interannual variation of the ITF in 2016, which is a unique event in the observational record.