Water column anomalies in dissolved silica over opaline Pelagic sediments and the origin of the deep silica maximum
Article first published online: 20 SEP 2012
Copyright 1979 by the American Geophysical Union.
Journal of Geophysical Research: Oceans (1978–2012)
Volume 84, Issue C12, pages 7809–7826, 20 December 1979
How to Cite
1979), Water column anomalies in dissolved silica over opaline Pelagic sediments and the origin of the deep silica maximum, J. Geophys. Res., 84(C12), 7809–7826, doi:10.1029/JC084iC12p07809., , , , and (
- Issue published online: 20 SEP 2012
- Article first published online: 20 SEP 2012
- Manuscript Accepted: 30 MAR 1979
- Manuscript Received: 31 MAR 1978
Recent estimates based on pore water studies and mass balance considerations put the average flux of dissolved silica from the sediments into the deep water at about 3 μmol cm−2 yr−1. This flux, if mixed uniformly in a bottom layer 100 m thick, results in an anomaly increment of 0.3 μmol kg−1 yr−1. In basins of restricted circulation containing opaline sediments the residence time of the bottom waters should be long enough that the resulting anomaly be easily resolvable using existing data. Examination of the many hundreds of detailed, precise silica profiles presently available in unpublished reports shows that this is indeed the case. The largest effects (∼50 μmol/kg) are seen in the Weddell-Enderby Basin. Intermediate anomalies (∼20 μmol/kg) are prevalent in the northern Indian Ocean. Lesser features (∼10 μmol/kg) are clearly discernable in the other antarctic basins and in the north Pacific. No anomalies are observed over the equatorial Pacific and Indian bands of opaline deposits, even in the basins east of the East Pacific Rise or in the Central Basin of the Indian Ocean. The flux of dissolved silica from the sea floor is generally unaccompanied by any resolvable oxygen consumption, indicating that relatively minor amounts of organic material reach the sediments in these regions. However, in the north Indian Ocean there are pronounced effects on all the nutrients, oxygen, and alkalinity, with regeneration approximating the Redfield prediction. In the northern Indian Ocean and the extreme northeast Pacific (northeast of 45°N, 160°W) the silica profiles increase to the bottom. This is a strong indication that the deep silica maximum observed over much of these oceans may have a large advective component, the feature itself being induced by the northward flow of the underlying low-silica bottom waters. In the Indian Ocean the data coverage is sufficient to demonstrate unequivocally the dominance of this effect.