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Edmond, JM, Jacobs SS, Gordon AL, Mantyla AW, Weiss RF.  1979.  Water column anomalies in dissolved silica over opaline pelagic sediments and the origin of the deep silica maximum. Journal of Geophysical Research-Oceans and Atmospheres. 84:7809-7826.   10.1029/JC084iC12p07809   AbstractWebsite

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 Examination of the many hundreds of detailed, precise silica profiles presently available in unpublished reports shows that this is indeed the case.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.

Fine, RA, Warner MJ, Weiss RF.  1988.  Water mass modification at the Agulhas retroflection: chlorofluoromethane studies. Deep-Sea Research Part a-Oceanographic Research Papers. 35:311-332.   10.1016/0198-0149(88)90013-1   AbstractWebsite

Chlorofluoromethane (CFM) and hydrographic data from the 1983 Agulhas Retroflection cruise are used to show the importance of the region in ventilating thermocline and Intermediate Waters of the southwest Indian ocean gyre. Generally South Atlantic waters are more recently ventilated by at least two years than those of the South Indian Ocean, probably because the latter are farther downstream from the source regions near the South Atlantic subantarctic sector. A two-component mixing model shows that the outflow from the Agulhas Retroflection (14-4°C) was composed of South Indian water and at least 23% South Atlantic water. However, at the density of Indian sector Subantarctic Mode Water the inflow into the Agulhas Retroflection was well preserved in the outflow, and the South Atlantic and Indian waters appear to be ventilated by different water masses. In addition, strong interleaving was found throughout the survey area (between 14 and 4°C), characterized by correlations of negative salinity anomalies with high CFM concentrations. At the density of Antarctic Intermediate Water (AAIW) there was interleaving of both low salinity water and higher salinity Red Sea Water. Using estimates of past atmospheric ratios of two CFMs, we calculate that AAIW within the retroflection was 50–75% diluted by mixing with CFM-free water since leaving the source region. Results from the two-component mixing model, which show substantial contributions of South Atlantic water in the outflow, suggest that the return flow for the 10 Sv leakage of Indian Ocean water via the Agulhas Current into the South Atlantic [Gordon (1985) Science, 227, 1030–1033; Gordonet al. (1987) Deep-Sea Research, 34, 565–600] is occurring at thermocline and intermediate depths. A combination of active mixing in this region and similarity in the ventilation processes may be the reason that the South Atlantic and Indian thermoclines are coincident in temperature and salinity space (between 15 and 7°C) as noted by Gordon.