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| Galbraith, Ed; Kienast, M; Pedersen, Tf; Calvert, Se. |
| An analysis of sedimentary nitrogen isotope records compiled from widely distributed marine environments emphasizes the global synchrony of denitrification changes and provides evidence for a strong temporal coupling of these variations to changes in nitrogen fixation as previously inferred. We explain the global coherence of these records by a simple physical control on the flux of dissolved oxygen to suboxic zones and the coupling to fixation via the supply of phosphorus to diazotrophs in suitable environments. According to our hypothesis, lower glacial-stage sea surface temperature increased oxygen solubility, while stronger winds in high-latitude regions enhanced the rate of thermocline ventilation. The resultant colder, rapidly flushed thermocline... |
| Tipo: Text |
Palavras-chave: Isotopes; Fixation; Denitrification. |
| Ano: 2004 |
URL: https://archimer.ifremer.fr/doc/00229/34026/32421.pdf |
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| Kienast, M; Higginson, Mj; Mollenhauer, G; Eglinton, Ti; Chen, Mt; Calvert, Se. |
| The bulk sedimentary nitrogen isotopic composition of two cores from nearby sites on the northern slope of the South China Sea ( Site 17940 and Ocean Drilling Program (ODP) Site 1144) differs by up to > 2 parts per thousand during the last glacial period. Given their close proximity, both core sites are located in the same biogeographic zone and nutrient regime, and it is thus unlikely that this offset is due to a true gradient in surface ocean conditions. In an attempt to resolve this offset, we have investigated the possible effects of two sedimentological parameters that can affect bulk sedimentary delta(15)N, namely, the variable contribution of inorganic N to bulk N in the sediment and the grain-size dependence of bulk delta(15)N. We find that... |
| Tipo: Text |
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| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00230/34076/32639.pdf |
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