Deep-water transit times in the eastern Indonesian basins, calculated from dissolved silica in deep and interstitial waters
Van Bennekom, A.J. (1988). Deep-water transit times in the eastern Indonesian basins, calculated from dissolved silica in deep and interstitial waters. Neth. J. Sea Res. 22(4): 341-354
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579; e-ISSN 1873-1406, more
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| Abstract |
The fiushing of the deep basins in the eastern Indonesian archipelago is studied by means of the dissolved silica (Si) distribution, using water column data from the Snellius-II Expedition as well as from the Indopac Expedition. The linear Θ-Si relationships below 500 to 1000 m permit the use of Si as a water-mass tracer. The main outflow of deep water from the Banda Sea into the Timor Trench is found east of Timor, above 1250 m depth, and the deeper parts of this outflow are partly recirculated through the Aru Basin and the Seram Sea into the north Banda Sea. Below the sill depth of the various basins, Θ remains about constant while Si gradually increases towards the bottom. The time needed to create this Si-excess is obtained with the Si-flux out of sediments, calculated from pore-water gradients. Deep-water transit times are 20 years for the Banda Sea, 2 to 15 years for smaller basins and 60 years for the intermittently flushed Weber Deep. Modelling the Si-excess with error functions in some small basins gives high diffusion coefficients of 45 to 150 cm²·s-1. The flux of Si from the sediments, 0.5 to 2 mol·m-2·a-1, is higher than in other deep-sea basins, it amounts to roughly 30% of the biogenic silica production in the euphotic zone. Dissolved Si at 20-40 cm depth in the sediments ranges from 450 to 590 mmol·m-3; about 2% of Al in biogenic silica from sediments might cause this apparently low solubility for sediments rich in biogenic silica. |
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