Ocean circulation through the Indonesian Seaway

The Indonesian throughflow (ITF) is thought to play an important role in global thermohaline circulation and influence global climate by funneling Pacific Warm Pool water into the Indian Ocean. Observations suggest the ITF is composed of North Pacific subtropical and thermocline waters that flow through Makassar Strait. At the southern end of Makassar St. most of the water flows eastward through the Flores Sea into the Banda Sea and then into the Indian Ocean.

Throughflow variability and flow volume is highly correlated with the state of ENSO. La Niña causes increased sea surface height in the Western Pacific Warm Pool region enhancing the dynamic height gradient with the Indian Ocean and therefore throughflow volume increases, the converse during El Niño is also true. The core of the ITF is also influenced by vertical mixing. Heat and freshwater are transported down toward the thermocline and cool water mixes upward resulting in potential influences on atmosphere-ocean heat flux . The ITF results in a significant export of heat and freshwater from the tropical Pacific into the Indian Ocean and may influence atmosphere-ocean coupling and tropical SST patterns and has the potential to impact the Asian Monsoon and ENSO. One way to examine the sources and variability of the throughflow is to use a water mass tracer. The radiocarbon ( D 14 C) content of waters can be used to track ocean currents, vertical mixing, and air-sea CO 2 exchange.

Measurements of sub-annual samples from coral skeletal material provide a proxy time-series record of the D 14 C of the dissolved inorganic carbon (DIC) of the surrounding seawater. This study will investigate interannual and decadal changes in tropical ocean circulation (including El Niño/Southern Oscillation) and advection of Pacific water masses through the Indonesian Seaway using a reconstruction of the spatial and temporal variability in 14 C distribution many decades into the past. We will focus on the acquisition of multi-decadal, high-resolution, high-precision ? 14 C time series from coral sites in the western Pacific and the Indonesian Seaway in order to study 1) variations in the proportion of waters mixing in the western tropical Pacific and 2) variability of the Indonesian throughflow itself and its relation to El Niño/Southern Oscillation.