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| Bourry, Christophe; Charlou, Jean-luc; Donval, Jean-pierre; Brunelli, M; Focsa, C; Chazallon, B. |
| Natural gas hydrates recovered from the Congo- Angola basin and Nigerian margins are analyzed by synchrotron X- ray powder diffraction. Biogenic methane is the most abundant gas trapped in the samples and others minor components (CO2, H2S) are co-clathrated in a type I cubic lattice structure. The refinement for the type I structure gives lattice parameters of a = 11.8646 ( 39) angstrom and a = 11.8619 ( 23) angstrom for specimens from Congo- Angola and Nigerian margins respectively at 90 K. These values, intermediate between the lattice constant of less pure methane specimens and pure artificial methane hydrates, indicate that lattice constants can be affected by the presence of encaged CO2, H2S and other gas molecules, even in small amounts. Thermal... |
| Tipo: Text |
Palavras-chave: Synchrotron X ray diffraction; Thermal expansion; Natural clathrate hydrates. |
| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/2007/publication-3511.pdf |
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| Lombard, Alix; Cazenave, Anny; Le Traon, Pierre-yves; Guinehut, Stephanie; Cabanes, Cecile. |
| In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840-842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions. However, recent investigations based on new ocean temperature data sets indicate... |
| Tipo: Text |
Palavras-chave: Ocean warming; Climate change; Thermal expansion; Sea level. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2201.pdf |
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