Interannual variability of the Indonesian Throughflow transport: A revisit based on 30 year expendable bathythermograph data

Abstract

AbstractBased on 30 year repeated expendable bathythermograph (XBT) deployments between Fremantle, Western Australia, and the Sunda Strait, Indonesia, from 1984 to 2013, interannual variability of geostrophic transport of the Indonesian Throughflow (ITF) and its relationships with El Niño Southern Oscillation (ENSO) and the Indian Ocean Dipole (IOD) are investigated. The IOD induced coastal Kelvin waves propagate along the Sumatra‐Java coast of Indonesia, and ENSO induced coastal Kelvin waves propagate along the northwest coast of Australia, both influencing interannual variations of the ITF transport. The ITF geostrophic transport is stronger during La Niña phase and weaker during El Niño phase, with the Niño3.4 index leading the ITF variability by 7 months. The Indian Ocean wind variability associated with the IOD to a certain extent offset the Pacific ENSO influences on the ITF geostrophic transport during the developing and mature phases of El Niño and La Niña, due to the covarying IOD variability with ENSO. The ITF geostrophic transport experiences a strengthening trend of about 1 Sv every 10 years over the study period, which is mostly due to a response to the strengthening of the trade winds in the Pacific during the climate change hiatus period. Decadal variations of the temperature‐salinity relationships need to be considered when estimating the geostrophic transport of the ITF using XBT data.