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Publication - Dr Joseph Stewart

    Intrareef variations in Li/Mg and Sr/Ca sea surface temperature proxies in the Caribbean reef‐building coral Siderastrea siderea

    Citation

    Fowell, SE, Sandford, K, Stewart, JA, Castillo, KD, Ries, JB & Foster, GL, 2016, ‘Intrareef variations in Li/Mg and Sr/Ca sea surface temperature proxies in the Caribbean reef‐building coral Siderastrea siderea’. Paleoceanography, vol 31., pp. 1315-1329

    Abstract

    Caribbean sea surface temperatures (SSTs) have increased at a rate of
    0.2°C per decade since 1971, a rate double that of the mean global
    change. Recent investigations of the coral Siderastrea siderea
    on the Belize Mesoamerican Barrier Reef System (MBRS) have demonstrated
    that warming over the last 30 years has had a detrimental impact on
    calcification. Instrumental temperature records in this region are
    sparse, making it necessary to reconstruct longer SST records indirectly
    through geochemical temperature proxies. Here we investigate the
    skeletal Sr/Ca and Li/Mg ratios of S. siderea from two distinct reef zones (forereef and backreef) of the MBRS. Our field calibrations of S. siderea
    show that Li/Mg and Sr/Ca ratios are well correlated with temperature,
    although both ratios are 3 times more sensitive to temperature change in
    the forereef than in the backreef. These differences suggest that a
    secondary parameter also influences these SST proxies, highlighting the
    importance for site- and species-specific SST calibrations. Application
    of these paleothermometers to downcore samples reveals highly uncertain
    reconstructed temperatures in backreef coral, but well-matched
    reconstructed temperatures in forereef coral, both between Sr/Ca-SSTs
    and Li/Mg-SSTs, and in comparison to the Hadley Centre Sea Ice and Sea
    Surface Temperature record. Reconstructions generated from a combined
    Sr/Ca and Li/Mg multiproxy calibration improve the precision of these
    SST reconstructions. This result confirms that there are circumstances
    in which both Li/Mg and Sr/Ca are reliable as stand-alone and combined
    proxies of sea surface temperature. However, the results also highlight
    that high-precision, site-specific calibrations remain critical for
    reconstructing accurate SSTs from coral-based elemental proxies.

    Full details in the University publications repository