Browsing by Author "Waelbroeck, Claire"
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- Atlantic circulation changes across a stadial-interstadial transitionPublication . Waelbroeck, Claire; Tjiputra, Jerry; Guo, Chuncheng; Nisancioglu, Kerim H.; Jansen, Eystein; Riveiros, Natalia Vazquez; Toucanne, Samuel; Eynaud, Frédérique; Rossignol, Linda; Dewilde, Fabien; Marches, Elodie; Lebreiro, Susana; Nave, SilviaABSTRACT: We combine consistently dated benthic carbon isotopic records distributed over the entire Atlantic Ocean with numerical simulations performed by a glacial configuration of the Norwegian Earth System Model with active ocean biogeochemistry in order to interpret the observed Cibicides delta C-13 changes at the stadial-interstadial transition corresponding to the end of Heinrich Stadial 4 (HS4) in terms of ocean circulation and remineralization changes. We show that the marked increase in Cibicides delta C-13 observed at the end of HS4 between similar to 2000 and 4200 m in the Atlantic can be explained by changes in nutrient concentrations as simulated by the model in response to the halting of freshwater input in the high-latitude glacial North Atlantic. Our model results show that this Cibicides delta C-13 signal is associated with changes in the ratio of southern-sourced (SSW) versus northern-sourced (NSW) water masses at the core sites, whereby SSW is replaced by NSW as a consequence of the resumption of deep-water formation in the northern North Atlantic and Nordic Seas after the freshwater input is halted. Our results further suggest that the contribution of ocean circulation changes to this signal increases from similar to 40 % at 2000 m to similar to 80 % at 4000 m. Below similar to 4200 m, the model shows little ocean circulation change but an increase in remineralization across the transition marking the end of HS4. The simulated lower remineralization during stadials compared to during interstadials is particularly pronounced in deep subantarctic sites, in agreement with the decrease in the export production of carbon to the deep Southern Ocean during stadials found in previous studies.
- Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamountPublication . Lebreiro, Susana M.; Peliz, Álvaro; Antón, Laura; Nave, Silvia; Reguera, M. Isabel; Lozano-Luz, Rocío; Waelbroeck, Claire; Crowhurst, Simon; Martrat, Belen; Lopez, Jordi F.; Hebert, Raphael; Lopez-Rodriguez, AlejandraABSTRACT: Turbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along-slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three deep cores covering up to 426,000 years in the Tore seamounts area. By evaluating a range of physical oceanographic mechanisms, the breaking of internal waves and mesoscale Mediterranean-eddies against unstable slopes in the seamounts area arises as the most likely triggers that precondition the recurrence pattern of the observed deep ocean turbidites.
- Evaluating the role of physical mechanisms as possible triggers for turbidity currents in a deep ocean seamount [Resumo]Publication . Lebreiro, Susana M.; Peliz, Álvaro; Antón, Laura; Nave, Silvia; Reguera, M. Isabel; Lozano-Luz, Rocío; Waelbroeck, Claire; Crowhurst, Simon; Martrat, Belen; Lopez, Jordi F.; Hebert, Raphael; Lopez-Rodriguez, AlejandraABSTRACT: Turbidity currents on continental margins are often attributed to cyclic climate variability and sea-level change, while the causes of deep ocean turbidites are as yet to be tested. The Atlantic Iberian margin provides a unique setting to contrast deep ocean and continental environments, including depression features that further protect from resuspension and erosion by along slope bottom currents. We present records of low-frequency, non-periodic, climate-independent turbidites from three exceptionally deep cores covering up to 426,000 years in the Tore seamounts area. Here we evaluate the possible role of a number of physical processes that, when combined, may induce sufficiently intense bottom boundary events and likely precondition the recurrence pattern of the observed deep ocean turbidites.