Change in the Indonesian Throughflow with the climatic shift of 1976/77

Abstract

A climate shift occurred in 1976 with Pacific equatorial temperatures experiencing a sharp rise and was first identified as a change in the background state of the El Nin˜o Southern Oscillation. The associated weakening of easterly trade winds across the Pacific led to our hypothesis that the Indonesian Throughflow (ITF) had also weakened. The change in volume transport of ITF before and after December 1975 was estimated using all the available subsurface temperature data on the IX1 expendable bathythermograph (XBT) line between Australia and Indonesia. Sea surface temperature (SST) rose by 1–2C, which could be due to increased air-sea heat flux and/or a change in regional circulation. A subsurface cooling in the main thermocline was attributed to a weakening of the Pacific trade winds. The South Equatorial Current (SEC) diminished in size and weakened in strength. The net westward volume transport between Australia and Indonesia showed a decrease of2.5 Sverdrups, or 23%. Citation: Wainwright, L., G. Meyers, S. Wijffels, and L. Pigot (2008), Change in the Indonesian Throughflow with the climatic shift of 1976/77