The first 15 year of INSTANT data reveal the complexities of the Indonesian throughflow

Abstract

passages allow for interocean exchange of water properties, which tend to reduce, though not remove, the thermohaline differences between the oceans. Such interocean exchange influences the heat and freshwater budgets of each ocean basin and in so doing represent an important part of the climate system. Most of the interocean exchange routes are at high latitudes, allowing for the establishment of the Antarctic Circumpolar Current and for low salinity surface water flow into the Arctic Sea by way of the Bering Strait. At mid-latitude there is leakage of subtropical Indian Ocean thermocline water into the South Atlantic around the southern rim of Africa. The Indonesian seas alone allow for an interocean exchange of tropical waters in what is referred to as the Indonesian Throughflow (ITF): a transfer of warm, relatively low salinity Pacific waters into the Indian Ocean. The ITF affects both oceans, though perhaps more so the thermohaline stratification of the smaller Indian Ocean. While the literature of the last 45 years offers a very wide range of annual mean transport values for the ITF, from near zero to 25 x 106 m3/sec, the more recent estimates narrow the range to 10 ± 5 x 106 m3/sec with large seasonal and intraseasonal variability (Wijffels and Meyers, 2002; Gordon, 2005).