The centennial and millennial variability of the IndoPacific Warm Pool and the Indonesian Throughflow

Abstract

As the only low-latitude connection between ocean basins, the Indonesian Throughflow allows the direct transmission of heat and salinity between the Pacific and Indian Oceans. The Mg/Ca and δ18O of calcite of Globigerinoides ruber (G. ruber) were used to estimate the sea surface temperature (SST) and δ18O of water, an indicator of hydrologic conditions, over the past 20,000 years. I also attempted to estimate thermocline structure using Pulleniatina obliquiloculata, but the Mg/Ca and δ18O of calcite data yield conflicting interpretations, indicating further work on this proxy is required. The G. ruber Mg/Ca results suggest that the SST of the outflow passages were influenced by high latitude Southern Hemisphere temperature. At approximately 10,000 years before present, there was a warming in the Makassar Strait. This local warming was coincident with the flooding of the Sunda Shelf, which opened a connection between the South China Sea and the Indonesian Throughflow. Regional δ18O of seawater reconstructions suggest that the mean position of the Intertropical Convergence Zone (ITCZ) was approximately the same as modern at the last glacial maximum and was displaced to the south during the Younger Dryas and Heinrich Stadial 1, suggesting the ITCZ responds to changes in the interhemispheric temperature gradient.