In this presentation, we use an eddy-resolving ocean model to assess the centennial changes of the Indonesian throughflow and the poleward temperature transport in South Indian Ocean during the 21st century in response to enhanced greenhouse warming. A significant decrease of poleward temperature transport in the Indian Ocean is captured in the downscaling ocean model, which can be primarily explained by the centennial decrease in the Indonesian Throughflow volume transport, which is associated with the weakening trend of the deep upwelling in the Pacific basin. The reduction of the Indonesian Throughflow drives the long term increase of the zonal thermocline depth differences between west and east boundaries, which causes anomalous northward geostrophic volume transport in subtropical Indian Ocean. The decrease of southward temperature transport at 32°S is mainly associated with the weakening of the Agulhas Current temperature transport, with additional contributions from a weakening Leeuwin Current. Based on a Sverdrup balance calculation, we demonstrate that the spin down of Indian Ocean subtropical gyre circulation associated with cyclonic wind stress curl changes is of secondary importance, compared to the direct influence from the Indonesian Throughflow, to the reduction of the Agulhas Current transport.

References:

Feng, M., Zhang, X., Sloyan, B. and Chamberlain, M., (2017), Contribution of the deep ocean to the centennial changes of the Indonesian Throughflow. Geophysical Research Letters, 44(6), pp.2859-2867.

Ma, J., Feng, M., Sloyan, B. Lan, J. (2018), Pacific influences on the meridional temperature transport of the Indian Ocean. Journal of Climate, under revision