988 resultados para Marion Prudlo
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Mode of access: Internet.
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Bibliography: p. 178-181.
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Mode of access: Internet.
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Following the launch of the "Marion Dufresne 1", first supply ship of the Terres Australes and Antarctiques Françaises and part time oceanographic vessel in the Indian Ocean, a new marine geology program was developped at the Laboratoire de Géologie, MNHN. The first oceanographic cruise of the "Marion Dufresne 1" started in 1973 in the Southwestern Indian Ocean (OSIRIS I cruise). Forty piston-cores recovered nearly 200 m of sediments consisting in the first of the 450 cores of the Indian Ocean collection now deposited at the Museum. L. Leclaire being Director from 1980 to 1991, a multidisciplinary team (including sedimentologists and micropaleontologists) was involved in many oceanographic cruises in the Indian Ocean. Marine sedimentology was developped during annual cruises programs in collaboration with geophysicists, geochemists, and biologists. In 1995, the "Marion Dufresne 2" replaced the initial "Marion Dufresne 1".
Underway physical oceanography and carbon dioxide measurements during Marion Dufresne cruise OISO_02
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General note: Title and date provided by Bettye Lane.
Underway physical oceanography and carbon dioxide measurements during Marion Dufresne cruise OISO_08
Underway physical oceanography and carbon dioxide measurements during Marion Dufresne cruise OISO_10
Underway physical oceanography and carbon dioxide measurements during Marion Dufresne cruise OISO_15
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Silicon isotopic signatures (d30Si) 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° S (northern Weddell Gyre). This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC). d30Si 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 (AASW), the Antarctic Intermediate Water (AAIW), and thermoclines in the low latitude areas. The residual silicic acid concentrations of end-members control the d30Si alteration of the mixing products and with the exception of AASW, all mixing interfaces have a highly Si-depleted mixed layer end-member. These processes deplete the silicic acid AASW concentration northward, across the different interfaces, without significantly changing the AASW d30Si composition. By comparing our new results with a previous study in the Australian sector we show that during the circumpolar transport of the ACC eastward, the d30Si composition of the silicic acid pools is getting slightly, but significantly lighter from the Atlantic to the Australian sectors. This results either from the dissolution of biogenic silica in the deeper layers and/or from an isopycnal mixing with the deep water masses in the different oceanic basins: North Atlantic Deep Water in the Atlantic, and Indian Ocean deep water in the Indo-Australian sector. This isotopic trend is further transmitted to the subsurface waters, representing mixing interfaces between the surface and deeper layers. Through the use of d30Si constraints, net biogenic silica production (representative of annual export), at the Greenwich Meridian is estimated to be 5.2 ± 1.3 and 1.1 ± 0.3 mol Si/m**2 for the Antarctic Zone and Polar Front Zone, respectively. This is in good agreement with previous estimations. Furthermore, summertime Si-supply into the mixed layer of both zones, via vertical mixing, is estimated to be 1.6 ± 0.4 and 0.1 ± 0.5 mol Si/m**2, respectively.