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| Crosta, X; Crespin, J; Billy, I; Ther, O. |
| In an effort to investigate the controlling factors behind Holocene delta C-13(org) changes in East Antarctica we report high-resolution down-core records of bulk organic matter carbon isotopic ratios (delta C-13(org)), diatom census counts, total organic carbon, and biogenic silica content taken from one core recovered in the Adelie Trough. A good correspondence between the delta C-13(org) record and records of small/large and pennate/centric ratios in many of the core segments indicates that diatom species composition affected Holocene delta C-13(org) variations, possibly via diatom shape and size effects. Variations in the surface water CO2 concentration and in the isotopic composition of the source during the Holocene cannot be ruled out although they... |
| Tipo: Text |
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| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00230/34080/32534.pdf |
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| Denis, Delphine; Crosta, X; Zaragosi, S; Romero, O; Martin, B; Mas, Virginie. |
| A 40 m long sediment core covering the 1000-9600 years BP period was retrieved from the Dumont d'Urville Trough off Adelie Land, East Antarctica, during the MD 130-Images X-CADO cruise. This sedimentary sequence allows the documentation of changes in climate seasonality during the Holocene. Here we show preliminary results of diatom communities, lithic grain distribution and titanium content measured on two 30 cm long sequences of thin sections. The two sequences originate from two different climate regimes, the colder Neoglacial and the warmer Hypsithermal. Proxies were measured at microscale resolution on 25 laminations for the Neoglacial and 14 laminations for the Hypsithermal. The two sequences reveal alternating light-green and dark-green laminae.... |
| Tipo: Text |
Palavras-chave: East Antarctica; Sea ice; Seasonality; Diatom ooze; Laminated sediments; Holocene; Adelie Land. |
| Ano: 2006 |
URL: http://archimer.ifremer.fr/doc/2006/publication-2275.pdf |
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| Crosta, X; Shemesh, A; Etourneau, J; Yam, R; Billy, I; Pichon, Jj. |
| Most high-southern latitude records of carbon and nitrogen isotopic ratios and elemental ratios are from the Antarctic and Polar Front zones, thus hindering a comprehensive view of nutrient cycling in the Southern Ocean. We present, for the first time, two records from the Subantarctic Zone and the southern Subtropical Zone of the Indian Ocean. These records provide a latitudinal transect covering the main oceanographic systems of the Southern Ocean. Carbon and nitrogen content of the diatom-bound organic matter increases during the last glacial in the Antarctic and Subantarctic zones but does not show a clear climate-related signal in the Subtropical Zone. Comparison of these records with sea-surface temperatures reconstructed at the core locations and... |
| Tipo: Text |
Palavras-chave: Diatoms; Nutrient cycling; Southern Ocean. |
| Ano: 2005 |
URL: https://archimer.ifremer.fr/doc/00230/34075/32543.pdf |
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| Ainley, Dg; Hobson, Ka; Crosta, X; Rau, Gh; Wassenaar, Li; Augustinus, Pc. |
| Here we present first time evidence for concordant variation in the isotopic signature at both the base and the upper levels of the Antarctic coastal food web during the Holocene. Laminae in sub-fossil deposits of snow petrel Pagodroina nivea stomach oil, known as mumiyo, were collected from nest-sites in the Bunger Hills, East Antarctica. Mumiyo layers were sub-sampled, radiocarbondated, and analyzed for delta C-13 and delta D. The obtained values were compared to isotopic variability among layers of an ocean sediment core collected, and similarly dated, in nearby Dumont D'Urville Trough. Overlapping records extended from about 10 160 to 526 calendar years before present (cal yr BP). Mumiyo delta D values remained relatively constant throughout the... |
| Tipo: Text |
Palavras-chave: Antarctica; Holocene climate change; Food webs; Isotopic analysis; Mumiyo; Pagodroma nivea; Sediment cores; Snow petrel. |
| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00496/60808/64708.pdf |
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| Crosta, X; Shemesh, A. |
| [1] Oceanic nutrient cycling in the Southern Ocean is supposed to have an important impact on glacial-interglacial atmospheric CO(2) changes and global climate. In order to characterize such nutrient cycling over the last two climatic cycles we investigated carbon and nitrogen isotopic ratios of diatom-bound organic matter (delta(13)C(diat) and delta(15)N(diat)- respectively) in two cores retrieved form the Atlantic and Indian sectors of the Antarctic Ocean. The two cores show the same isotopic patterns. The delta(13)C(diat) values are depleted during glacial periods and enriched during interglacial periods, indicating lower productivity during cold times. The delta(15)N(diat) values are enriched during glacial periods and depleted during interglacial... |
| Tipo: Text |
Palavras-chave: Southern Ocean; Paleoceanography; Geochemistry; Diatoms. |
| Ano: 2002 |
URL: https://archimer.ifremer.fr/doc/00223/33402/31859.pdf |
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