Arlindo Circulation: A Study of the Indonesian Sea's Circulation and Mixing. The Inverted Echo Sounder Component

The Arlindo Project ("Arlindo" is an acronym for Arus Lintas Indonen, meaning 'throughflow' in Bahasa Indonesia) is a joint oceanographic research endeavor of Indonesia and the United States. Arlindo has as its primary goal to study the circulation and water mass stratification within the Indonesian Seas in order to formulate a thorough description of the source, spreading patterns, interocean transport and dominant mixing processes. The Indonesian Seas are important in terms of both local and larger scale ocean phenomena. The magnitude and variations of the Pacific to Indian Ocean throughflow is considered a key element in the thermohaline balance of the Indian and Pacific Oceans, and perhaps even to the global climate system. Indonesian oceanographic features may influence ENSO by governing the "seepage" of the western tropical Pacific warm pool water into the Indian Ocean. It provides an interactive link between the warm tropical water of these oceans. Furthermore advective and tidal induced mixing may govern to some extent the SST and sea-air coupling, with feedback on ENSO. The main objective of this work was to deploy an array of instruments to measure the throughflow across the Makassar Strait. The choice of the strait was based in previous results (Gordon and Fine, 1995) that proved that most of the throughflow from the Pacific to the India Ocean occurs through this strait. The main fieldwork consists of the deployment of current meter moorings, some of them equipped with temperature pods, inverted echo sounders, pressure gauges and hydrographic surveys including acoustic Doppler profiling and tracers. This Program was funded to carry out the inverted echo sounder (IES) component of Arlindo. As part of this grant, four inverted echo sounders equipped with pressure gauges (PIES) were deployed along the main axis of the Makassar strait bracketing the current meter mooring.