Suppressed Changes of the Makassar Strait Throughflow During the 2020–2023 “Triple-Dip” La Niña by Indian Ocean Winds

Abstract

As a crucial component of global ocean circulation, the Indonesian Throughflow (ITF) is modulated by the El Niño-Southern Oscillation. While multi-year La Niña events often greatly enhance the volume transport of the ITF, the 2020–2023 La Niña caused only a modest increase in the ITF via Makassar Strait—0.3 Sv above the climatology of 12 Sv. Dominated by the 0–400 m velocity variations, the relatively weak transport is attributed to a milder Pacific easterly wind due to a weaker La Niña intensity. The strong negative Indian Ocean Dipole accompanying the third-year La Niña induced the intensifying westerlies and anomalously elevated sea level over the eastern Indian Ocean during 2020–2023. Model experiments show that the Indian Ocean wind reduced the Pacific-originated ITF inflow variability by 51% in 2020–2023. With the increasing frequency of multi-year La Niña events, this study highlights the influence of Indian Ocean wind-driven dynamics in modulating the ITF transport.