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| Planchon, F.; Cavagna, A-j.; Cardinal, Damien; Andre, L.; Dehairs, F.. |
| As part of the GEOTRACES Bonus-GoodHope (BGH) expedition (January-March 2008) in the Atlantic sector of the Southern Ocean, particulate organic carbon (POC) export was examined from the surface to the mesopelagic twilight zone using water column distributions of total Th-234 and biogenic particulate Ba (Ba-xs). Surface POC export production was estimated from steady state and non steady state modelling of Th-234 fluxes, which were converted into POC fluxes, using the POC/Th-234 ratio of large, potentially sinking particles (>53 mu m) collected via in situ pumps. Deficits in Th-234 activities were observed at all stations from the surface to the bottom of the mixed layer, yielding Th-234 export fluxes from the upper 100 m of 496 +/- 214 dpm m(-2) d(-1)... |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00181/29206/27580.pdf |
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| Bayon, Germain; Delvigne, C.; Ponzevera, Emmanuel; Borges, A. V.; Darchambeau, F.; De Deckker, P.; Lambert, T.; Monin, L.; Toucanne, Samuel; Andre, L.. |
| The δ30Si stable isotopic composition of silicon in soils and fine-grained sediments can provide insights into weathering processes on continents, with important implications on the Si budget of modern and past oceans. To further constrain the factors controlling the distribution of Si isotopes in sediments, we have analysed a large number (n=50) of separate size-fractions of sediments and suspended particulate materials collected near the mouth of rivers worldwide. This includes some of the world’s largest rivers (e.g. Amazon, Congo, Mackenzie, Mississippi, Murray-Darling, Nile, Yangtze) and rivers from the case study areas of the Congo River Basin and Northern Ireland. Silt-size fractions exhibit a mean Si isotopic composition (δ30Si = -0.21 ± 0.19‰; 2... |
| Tipo: Text |
Palavras-chave: World rivers; Congo basin; Northern Ireland; Si isotopes; Clay minerals; Weathering; Temperature; Precipitation. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00434/54609/55991.pdf |
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| Jacquet, Shm; Dehairs, F.; Lefevre, D.; Cavagna, A. J.; Planchon, F.; Christaki, U.; Monin, L.; Andre, L.; Closset, I.; Cardinal, D.. |
| We report on the zonal variability of mesopelagic particulate organic carbon remineralization and deep carbon transfer potential during the Kerguelen Ocean and Plateau compared Study 2 expedition (KEOPS 2; October-November 2011) in an area of the polar front supporting recurrent massive blooms from natural Fe fertilization. Mesopelagic carbon remineralization (MR) was assessed using the excess, non-lithogenic particulate barium (Ba-xs) inventories in mesopelagic waters and compared with bacterial production (BP), surface primary production (PP) and export production (EP). Results for this early season study are compared with the results obtained during a previous study (2005; KEOPS 1) for the same area at a later stage of the phytoplankton bloom. Our... |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00260/37140/35670.pdf |
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| Fripiat, F.; Cavagna, A. -j.; Dehairs, F.; Speich, Sabrina; Andre, L.; Cardinal, D.. |
| Silicon isotopic signatures (delta(30)Si) of water column silicic acid (Si(OH)(4)) were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone) down to 57 degrees S (northern Weddell Gyre). This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC). delta(30)Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water... |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00052/16298/13811.pdf |
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| Bayon, Germain; Toucanne, Samuel; Skonieczny, Charlotte; Andre, L.; Bermell, Sylvain; Cheron, Sandrine; Dennielou, Bernard; Etoubleau, Joel; Freslon, Nicolas; Gauchery, T.; Germain, Yoan; Jorry, Stephan; Menot, G.; Monin, L.; Ponzevera, Emmanuel; Rouget, M. -l.; Tachikawa, K.; Barrat, Jean-alix. |
| Over the past decades, rare earth elements (REE) and their radioactive isotopes have received tremendous attention in sedimentary geochemistry, as tracers for the geological history of the continental crust and provenance studies. In this study, we report on elemental concentrations and neodymium (Nd) isotopic compositions for a large number of sediments collected near the mouth of rivers worldwide, including some of the world’s major rivers. Sediments were leached for removal of non-detrital components, and both clay and silt fractions were retained for separate geochemical analyses. Our aim was to re-examine, at the scale of a large systematic survey, whether or not REE and Nd isotopes could be fractionated during Earth surface processes. Our results... |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00276/38733/37249.pdf |
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| Fripiat, F.; Cavagna, A. -j.; Dehairs, F.; De Brauwere, A.; Andre, L.; Cardinal, D.. |
| Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO(2) variation. In this context, the natural silicon isotopic composition (delta Si-30) of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (Bonus-GoodHope) which includes for the first time summer delta Si-30 signatures of suspended biogenic silica (i) for the whole water column at three stations and (ii) in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal... |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00226/33769/32565.pdf |
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