HR: 0830h
AN: PP11A-0195    [PDF]
TI: Deep-Sea Corals: a New Tool to Track Intermediate Water Masses Variability
AU: * Lutringer, A
EM: lutringer@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, Campus du CNRS Avenue de la Terrasse, Gif sur Yvette, 91 198 ced France
AU: Blamart, D
EM: blamart@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, Campus du CNRS Avenue de la Terrasse, Gif sur Yvette, 91 198 ced France
AU: Frank, N
EM: Norbert.Frank@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, Campus du CNRS Avenue de la Terrasse, Gif sur Yvette, 91 198 ced France
AU: Labeyrie, L
EM: labeyrie@lsce.cnrs-gif.fr
AF: Laboratoire des Sciences du Climat et de l'Environnement, Campus du CNRS Avenue de la Terrasse, Gif sur Yvette, 91 198 ced France
AB: Intermediate water masses in the North Atlantic Ocean are affected by strong seasonal mixings but their variability during climate change is still to be explored. One of the more suitable tools to record this variability are deep-sea corals, because they record continuously sea water parameters in their aragonitic skeleton. Unfortunately they do not precipitate their skeleton at isotopic equilibrium with sea-water. The positive linear regression existing between $\delta^{18}$O and $\delta^{13}$C is not easily interpretable in terms of environmental parameters. We have used Smith et al. 2000 calibration combined with Shackleton 1974 paleo-temperature equation to interpret the isotopic signal (C and O) contained in deep-sea corals. Knowing the value of $\delta^{13}$C in seawater we can determine the corresponding value of $\delta^{18}$O along the regression line for each coral. This value is then corrected for the fractionation between aragonite and calcite and it can be used in the equation established by Epstein et al. 1953 and later rewritten by Shackleton 1974 to find a temperature. The method has then been applied to corals (Lophelia pertusa) coming from different cores collected in the Porcupine and Rockall banks at about 750m depth. The sampling was made with a micro-sampler to take into account the distribution of isotopes in the different aragonite crystal forms. These isotopic analysis lead us to a relationship between the $\delta^{18}$O value of the coral, the $\delta^{18}$O of seawater and the temperature. As the corals have been dated with the $^{230}$Th/U method, the different isotopic values can be placed in a Temperature/Salinity diagram in order to estimate the relative contribution of the various water masses in the Porcupine and Rockall banks along time. This new approach offers the possibility to track intermediate water masses variability.
DE: 4267 Paleoceanography
DE: 4870 Stable isotopes
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting