Propriétés géochimiques et isotopiqes des sédiments du détroit de Fram, Océan Arctique. Implications paléocéanographiques et paléoclimatiques

Abstract : Freshwater exports (sea-ice and oceanic currents) from the Arctic Ocean to the nordic seas is a critical component of the Atlantic Meridional Overturning Circulation and hence of the climatic system. Factors controling those exports are still partially unknown. An indirect way of tracing the intensity and patterns of sea-ice circulation is to trace the origin of the sediments it carries and that settle along the main drift routes towards the North Atlantic. We hence document a direct sedimentary flux that is linked to the detrital particle matrices. Another flux, this one being indirect, comes from the dissolved elements that adsorb onto particles along continental margins where sedimentary fluxes are the highest. We have extracted the authigenic (dissolved) phase from the sediment in order document the evolution of water-masses in Fram Strait since the last glacial maximum. Pb, Nd and Sr isotopic data allowed us to identify two sedimentary sources from the late glacial to the onset of the younger Dryas : canadian and western russian margins, then covered by large ice sheets. After the Younger Dryas however, sedimentary supplies originate from several sources including Greeland, Chukchi Sea and East Siberian Sea margins. The authigenic phase displays a change from 19.8 to 16.4 ka likely linked to the early deglaciation of the Eurasian ice sheet. More recently, [Epsilon]Nd values reflect a more important contribution from the Pacific on water masses exiting through Fram Strait
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Jenny Maccali. Propriétés géochimiques et isotopiqes des sédiments du détroit de Fram, Océan Arctique. Implications paléocéanographiques et paléoclimatiques. Sciences de la Terre. Université de Lorraine, 2012. Français. ⟨NNT : 2012LORR0347⟩. ⟨tel-01750037⟩

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