Contribution of the Karimata Strait transport to the Indonesian Throughflow as seen from a data assimilation model

• We examined the destinations of the Karimata Strait transport Karimata Strait transport.
• Seasonally, the Karimata Strait transport is an important component to the Indonesian Throughflow.
• ENSO and Indian Ocean Dipole modulate Karimata Strait transport interannually.
• Waters from the Karimata Strait transport can also enter the Pacific.

A particle-tracking experiment based on Bluelink ReANalysis (BRAN) is designed to explore the contribution of a branch of the South China Sea Throughflow, the Karimata Strait (KS) transport, to the Indonesian Throughflow (ITF) from the Pacific to the Indian Ocean. Results of the particle-tracking experiment show that most of the KS transport enters the Indian Ocean during the first half of a calendar year, with a maximum transport of more than 3 Sv in March–April. The annual average contribution of the KS transport to the ITF is 1.6 Sv, 13% of the annual mean ITF transport, while in February–April, the contribution is above 20%. Interannual variations of the KS transport into the Indian Ocean are modulated by the El Niño-Southern Oscillation (ENSO). More SCS waters through KS can enter the Indian Ocean during El Niño phase, and less SCS waters through KS can enter the Indian Ocean during La Niña phase. SCS waters through KS can also enter the Pacific, especially during La Niña and negative Indian Ocean Dipole phase.