A strong sub-thermocline intrusion of the North Equatorial Subsurface Current into the Makassar Strait in 2016-2017

Abstract:

The transfer of waters from the tropical Pacific to the Indian Ocean via the Indonesian Throughflow (ITF), the majority of which flows through the Makassar Strait, plays an important role in global ocean circulation and climate variation. Here, we investigate the poorly understood sub-thermocline pathway from the Pacific to the Makassar Strait by examining an observed strong intrusion of Pacific waters in the sub-thermocline Makassar Strait in 2016-2017 in the aftermath of a strong El Niño, which enhanced the sub-thermocline transport to match the transport above the thermocline. Water mass analyses suggest that the source of the sub-thermocline intrusion is a mixture of intermediate-depth waters from both the North and the South Pacific. Geostrophic currents of the Argo profiles and reanalysis data suggest that the sub-thermocline intrusion of the Makassar Strait is drawn from the North Equatorial Subsurface Current, which was particularly strong in 2016-2017. These results are anticipated to be the beginning of more comprehensive investigations of the Indo-Pacific Ocean sub-thermocline connection.