Wu Henry C.

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Wu
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Henry C.
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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
    Tropical sea surface temperatures for the past four centuries reconstructed from coral archives
    (John Wiley & Sons, 2015-03-18) Tierney, Jessica E. ; Abram, Nerilie J. ; Anchukaitis, Kevin J. ; Evans, Michael N. ; Giry, Cyril ; Kilbourne, K. Halimeda ; Saenger, Casey P. ; Wu, Henry C. ; Zinke, Jens
    Most annually resolved climate reconstructions of the Common Era are based on terrestrial data, making it a challenge to independently assess how recent climate changes have affected the oceans. Here as part of the Past Global Changes Ocean2K project, we present four regionally calibrated and validated reconstructions of sea surface temperatures in the tropics, based on 57 published and publicly archived marine paleoclimate data sets derived exclusively from tropical coral archives. Validation exercises suggest that our reconstructions are interpretable for much of the past 400 years, depending on the availability of paleoclimate data within, and the reconstruction validation statistics for, each target region. Analysis of the trends in the data suggests that the Indian, western Pacific, and western Atlantic Ocean regions were cooling until modern warming began around the 1830s. The early 1800s were an exceptionally cool period in the Indo-Pacific region, likely due to multiple large tropical volcanic eruptions occurring in the early nineteenth century. Decadal-scale variability is a quasi-persistent feature of all basins. Twentieth century warming associated with greenhouse gas emissions is apparent in the Indian, West Pacific, and western Atlantic Oceans, but we find no evidence that either natural or anthropogenic forcings have altered El Niño–Southern Oscillation-related variance in tropical sea surface temperatures. Our marine-based regional paleoclimate reconstructions serve as benchmarks against which terrestrial reconstructions as well as climate model simulations can be compared and as a basis for studying the processes by which the tropical oceans mediate climate variability and change.