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Theses

Reconstruction de la variabilité des eaux intermédiaires par l'étude géochimique des coraux profonds

Abstract : 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 developing new archives, such as deep-water corals,
which can be precisely dated and monitor intermediate water composition for these high current speed
environments on the shelf break if we are about to reconstruct intermediate water masses changes in
the north-eastern North Atlantic.
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https://tel.archives-ouvertes.fr/tel-00159102
Contributor : Audrey Lutringer-Paquet <>
Submitted on : Monday, July 2, 2007 - 12:07:43 PM
Last modification on : Thursday, August 6, 2020 - 4:32:24 PM
Long-term archiving on: : Thursday, April 8, 2010 - 6:33:52 PM

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  • HAL Id : tel-00159102, version 1

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Audrey Lutringer-Paquet. Reconstruction de la variabilité des eaux intermédiaires par l'étude géochimique des coraux profonds. Océan, Atmosphère. Université Paris Sud - Paris XI, 2005. Français. ⟨tel-00159102⟩

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