The Indonesian Throughflow (ITF) links two oceans and in so doing provides a pathway for modifying the stratification within each of these oceans as well as sea-air fluxes that impact on such climate phenomena as ENSO and the Asian Monsoon. While a number of measurement programs have recently been undertaken in the Indonesian region, a serious shortcoming is their lack of temporal coherence: the data cover different time periods and depths in the different passages of the complex pathways linking the Pacific and Indian Oceans. This has lead to ambiguity of the mean and variable nature of the ITF, and of the transformation of the thermohaline and transport profiles within the interior seas.

The INSTANT program offers the opportunity to finally measure in a coordinated fashion the ITF in the key throughflow passages simultaneously. Involving contributions of 5 countries (USA, France, Netherlands, Australia, Indonesia), the measurements span a 3 year period beginning in late 2003.

The INSTANT objectives are: 1) To determine the full depth velocity and property structure of the Throughflow and its associated heat and freshwater flux; 2) To resolve the annual, seasonal, and intraseasonal characteristics of the ITF transport and property flux; 3) To investigate the storage and modification of the ITF waters within the internal Indonesian seas, from their Pacific source characteristics to the Indonesian Throughflow water exported into the Indian Ocean; and 4) To contribute to the design of a cost-effective, long-term monitoring strategy for the ITF.