Indonesian Throughflow

The Indonesian Throughflow (ITF) refers to the transfer of upper ocean waters from the Pacific to the Indian Ocean through the Indonesian Seas. ITF flow varies seasonally in response to the monsoons, and is also correlated with interannual variations in the Pacific (El Nino/Southern Oscillation). Variations in the ITF affect the properties, and climate of both the Indian and Pacific Oceans, and may also feedback and influence ENSO. It is not known whether the ITF has varied in the past, and if so, the effect of these variations on regional and global climate.

In 2003, we collected sediment cores from the Indonesian Seas in order to reconstruct past changes in the Indonesian Throughflow (ITF) and climate of the region. We collaborated with Indonesian scientists and used the R/V Baruna Jaya VIII, an Indonesian vessel. WHOI's Jim Broda designed a coring rig, capable of taking multicores and gravity cores for the vessel.

As most of the ITF transport occurs in the thermocline, most of the cores we collected were from thermocline depths. Work in our labs confirms that many of the cores we collected have high accumulation rates (even in excess of 100cm/kyr), and many have modern core-tops. We use the chemistry of benthic foraminifera in thermocline-depth cores to reconstruct changes in the ITF at decadal resolution during the Holocene. We also use the chemistry of planktonic foraminifera to reconstruct surface hydrography, and by measuring the chemistry of thermocline dwellers, a second measure of thermocline depth and properties. We have also collaborated with modelers (Dr. Caroline Ummenhofer and Dr. Shawn Wang) to understand drivers of ITF changes.