TY - JOUR T1 - Evidence for calcification depth change of Globorotalia truncatulinoides between deglaciation and Holocene in the Western Atlantic Ocean JF - Marine Micropaleontology Y1 - 2009 A1 - Cleroux, C. A1 - Lynch-Stieglitz, J. A1 - Schmidt, M. W. A1 - Cortijo, E. A1 - Duplessy, J. C. AB - Measurements of the delta O-18 in tests of planktonic and benthic foraminifera in the Florida Straits are used to reconstruct the properties of the water column through time over the last 12 ka (Lynch-Stieglitz et al., in press). The isotopic composition of the foraminifera largely reflects the vertical density gradient. We use this reconstruction and delta O-18 measurements on Globorotalia truncatulinoides in a nearby core to track the depth habitat of this species from the last deglaciation to 1.6 ka B.P. Around 9 ka, G. truncatulinoides was calcifying in much shallower water than during the late Holocene. The downward migration toward its modem habitat is a regional phenomenon over the western tropical Atlantic continental slope. The cause is still unclear but we hypothesize that the shallower calcification depth may be a response to the presence of glacial melt water or to circulation changes. This study points to the value of further study of the ecology, life cycle and calcification depth for G. truncatulinoides and other planktonic foraminifera that are used to reconstruct the history of the thermocline and upper water column structure. Published by Elsevier B.V. VL - 73 IS - 1-2 N1 - id: 1883; 514BR Times Cited:0 Cited References Count:33Y JO - Evidence for calcification depth change of Globorotalia truncatulinoides between deglaciation and Holocene in the Western Atlantic Ocean ER - TY - JOUR T1 - Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation JF - Earth and Planetary Science Letters Y1 - 2005 A1 - Gherardi, J. M. A1 - Labeyrie, L. A1 - McManus, J. F. A1 - Francois, R. A1 - Skinner, L. C. A1 - Cortijo, E. AB - A first study from the subtropical western Atlantic, using Pa-231/Th-230 ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary Pa-231/Th-230 ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured Pa-231/Th-230 in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Ben-nuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary Pa-231/Th-230 ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fermoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment Pa-231/Th-230 in different sections of the Atlantic Ocean. (C) 2005 Elsevier B.V. All rights reserved. VL - 240 IS - 3-4 N1 - 995vhTimes Cited:93Cited References Count:69 JO - Evidence from the Northeastern Atlantic basin for variability in the rate of the meridional overturning circulation through the last deglaciation ER -