Caillon Nicolas

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Caillon
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Nicolas
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  • Article
    Interlaboratory study for coral Sr/Ca and other element/Ca ratio measurements
    (John Wiley & Sons, 2013-09-23) Hathorne, Ed C. ; Gagnon, Alexander C. ; Felis, Thomas ; Adkins, Jess F. ; Asami, Ryuji ; Boer, Wim ; Caillon, Nicolas ; Case, David H. ; Cobb, Kim M. ; Douville, Eric ; deMenocal, Peter B. ; Eisenhauer, Anton ; Garbe-Schonberg, Dieter ; Geibert, Walter ; Goldstein, Steven L. ; Hughen, Konrad A. ; Inoue, Mayuri ; Kawahata, Hodaka ; Kolling, Martin ; Cornec, Florence L. ; Linsley, Braddock K. ; McGregor, Helen V. ; Montagna, Paolo ; Nurhati, Intan S. ; Quinn, Terrence M. ; Raddatz, Jacek ; Rebaubier, Helene ; Robinson, Laura F. ; Sadekov, Aleksey ; Sherrell, Robert M. ; Sinclair, Dan ; Tudhope, Alexander W. ; Wei, Gangjian ; Wong, Henri ; Wu, Henry C. ; You, Chen-Feng
    The Sr/Ca ratio of coral aragonite is used to reconstruct past sea surface temperature (SST). Twenty-one laboratories took part in an interlaboratory study of coral Sr/Ca measurements. Results show interlaboratory bias can be significant, and in the extreme case could result in a range in SST estimates of 7°C. However, most of the data fall within a narrower range and the Porites coral reference material JCp-1 is now characterized well enough to have a certified Sr/Ca value of 8.838 mmol/mol with an expanded uncertainty of 0.089 mmol/mol following International Association of Geoanalysts (IAG) guidelines. This uncertainty, at the 95% confidence level, equates to 1.5°C for SST estimates using Porites, so is approaching fitness for purpose. The comparable median within laboratory error is <0.5°C. This difference in uncertainties illustrates the interlaboratory bias component that should be reduced through the use of reference materials like the JCp-1. There are many potential sources contributing to biases in comparative methods but traces of Sr in Ca standards and uncertainties in reference solution composition can account for half of the combined uncertainty. Consensus values that fulfil the requirements to be certified values were also obtained for Mg/Ca in JCp-1 and for Sr/Ca and Mg/Ca ratios in the JCt-1 giant clam reference material. Reference values with variable fitness for purpose have also been obtained for Li/Ca, B/Ca, Ba/Ca, and U/Ca in both reference materials. In future, studies reporting coral element/Ca data should also report the average value obtained for a reference material such as the JCp-1.
  • Article
    Constraining ventilation during deepwater formation using deep ocean measurements of the dissolved gas ratios 40Ar/36Ar, N2/Ar, and Kr/Ar
    (American Geophysical Union, 2010-11-19) Nicholson, David P. ; Emerson, Steven ; Caillon, Nicolas ; Jouzel, Jean ; Hamme, Roberta C.
    The concentration of inert gases and their isotopes in the deep ocean are useful as tracers of air-sea gas exchange during deepwater formation. ΔKr/Ar, ΔN2/Ar, and δ40Ar were measured in deep profiles of samples collected in the northwest Pacific, subtropical North Pacific and tropical Atlantic oceans. For the ocean below 2000 m, we determined a mean ΔKr/Ar composition of −0.96% ± 0.16%, a mean ΔN2/Ar of 1.29% ± 0.21% relative to equilibrium saturation, and for δ40Ar a value of 1.188‰ ± 0.055‰ relative to air. These data are used to constrain high-latitude ventilation processes in the framework of three-box and seven-box ocean models. For the three-box model tracer data, we constrain the appropriate surface area of the high-latitude region in both models to be 3.6% (+2.5%, −1.7%) of ocean surface area and the bubble air injection rate to be 22.7 (+8.8, −7.3) mol air m−2 yr−1. Results for the seven-box model were similar, with a high-latitude area of 3.3% (+2.2%, −1.3%). Our results provide geochemical support for suggestions that the effective area of high-latitude ventilation is much smaller than the region of elevated preformed nutrients and demonstrate that noble gases strongly constrain the ocean solubility pump. Reducing high-latitude surface area weakens the CO2 solubility pump in the box models and limits communication between the atmosphere and deep ocean. These tracers should be useful constraints on high-latitude ventilation and the strength of the solubility pump in more complex ocean general circulation models.