Restoration of the North-east Atlantic and Mediterranean Sea hydrology from the neodymium isotopes since the last glacial period

• Main Author: Dubois-Dauphin, Quentin
• Other Authors: Géosciences Paris Sud (GEOPS), Université Paris-Sud - Paris 11 (UP11)-Centre National de la Recherche Scientifique (CNRS), Université Paris Saclay (COmUE), Christophe Colin
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2016
• Subjects: Neodymium isotopes; Cold-Water corals; Mediterranean Sea; North-East Astlantic; Composition isotopique du Nd; Coraux d'eau froide; Atlantique nord; Mer Mediterranée; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDU.STU.OC]Sciences of the Universe [physics]/Earth Sciences/Oceanography; Dansgaard-Oeschger events; North Atlantic; North East Atlantic
• Online Access: https://theses.hal.science/tel-01404733; https://theses.hal.science/tel-01404733/document; https://theses.hal.science/tel-01404733/file/78158_DUBOIS-DAUPHIN_2016_diffusion.pdf

: The purpose of this thesis is to constrain the hydrology of the North-East Atlantic and western Mediterranean Sea since the last glacial period from neodymium isotopic composition (εNd) measured on seawater, cold water corals and foraminifera. In particular, hydrological changes of intermediate water masses (LIW, AAIW, MSW, mid-subtropical and subpolar gyre water) have been studied as their role on salt budget in North Atlantic and ultimately on AMOC are currently poorly constrained. This work has been conducted at times of major and abrupt hydrological changes that occurred during rapid climatic variations of the last glacial period (Heinrich and Dansgaard-Oeschger events) and during the last sapropel deposit (S1) in eastern Mediterranean Sea. In a first step, we have improved the spatial distribution of water masses εNd values in North-east Atlantic and Alboran Sea, what is an absolute prerequisite in order to track past hydrological changes in these areas with εNd proxy. Next, we have highlighted a major change of the western Mediterranean circulation pattern during the sapropel S1 deposit, which is marked south of Sardinia by a strong reduction of eastern-sourced water masses (LIW) in favor of western-sourced water masses (WIW). This hydrological change as well as those occurring in Mediterranean Sea since the last glacial period was not associated with strong modifications of εNd values in Alboran and Balearic Sea, suggesting a stability of Nd isotopic signature of MOW over the time. This has highlighted, from an εNd record obtained on cold water corals in the Gulf of Cadiz, an enhanced contribution of more radiogenic AAIW and therefore a stronger northward penetration in North Atlantic at times of reduced AMOC linked to iceberg discharges from Northern Hemisphere ice sheets. L’objectif de cette thèse est d’apporter de nouvelles contraintes sur l’hydrologie de l’Atlantique Nord-Est et de la Méditerranée occidentale depuis la dernière période glaciaire à partir de l’analyse de la composition isotopique ...