Reconstruction of intermediate water masses variability through deep-sea coral geochemistry

• Main Author: Lutringer-Paquet, Audrey
• Other Authors: Laboratoire des Sciences du Climat et de l'Environnement Gif-sur-Yvette (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA), Université Paris Sud - Paris XI, Laurent Labeyrie([e-mail]), Ecomound, Geomound
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2005
• Subjects: Deep-sea corals; stable isotopes (C-O); intermediate water; carbonate mounds; North Atlantic; coraux profonds; isotopes stables (C et O); eaux intermédiaires; monts carbonatés; Atlantique Nord; [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; Porcupine Seabight; Rockall Bank; Rockall Trough; Labrador Sea
• Online Access: https://theses.hal.science/tel-00159102; https://theses.hal.science/tel-00159102/document; https://theses.hal.science/tel-00159102/file/theseLUTRINGER-PAQUET.pdf

The interaction between the intermediate water masses and rapid climate changes is becoming a hot topic in paleoclimatology. However, the mechanisms involved in such connection are still to be explored due to the lack of reliable records. The aim of this study was to further develop the use of deep-water corals and their isotopic composition to reconstruct paleoceanographic variations of intermediate water masses. First, the method recently proposed in the literature to retrieve paleotemperature from deep-water coral's isotopic composition has been reviewed and tested with six living deep-water corals. Second, the method has been applied to a long sediment core collected in the Rockall Bank (SE Ireland) and filled with corals skeletons. The observed isotopic variability of corals along the cores has been interpreted as changes in the relative contribution of the Mediterranean overflow water relative to the Labrador Sea water at intermediate depth within Rockall Trough. The connection with atmospheric signals shows that these changes might be the consequences of North-Atlantic-Oscillations-(NAO)- like variations occurring during the Holocene. Deep-water coral's sensitivity to environmental changes has been explored by high precision 230Th/U dating of corals from four sediment cores collected on Rockall Bank and in Porcupine Seabight. No evidence has been found for coral growth during glacial periods at these sites and a scenario of coral's retreat to southern latitudes has been proposed according to results recently published. This scenario highlights the sensitivity of corals to hydrographic and climatic variations and its implications on the growth's dynamic of carbonate mounds. Besides, the comparison of co-located corals and foraminifers shows the complexity of the sedimentary pattern in the Rockall Bank and the Porcupine Seabight, as foraminifers are not coeval to coral growth and thus clear indicate re-distribution of sediments in areas of high bottom water currents. This demonstrates the importance of ...