Calibration of sclerosponge oxygen isotope records to temperature using high-resolution δ18O data

A revised calibration is presented relating the oxygen isotope composition of the aragonite-secreting sclerosponge Ceratoporella nicholsoni, oxygen isotope composition of seawater, and ambient water temperature. This new relationship has been obtained using high-resolution δ18O data measured in sclerosponges from the Bahamas and Jamaica compared to ambient temperature measurements and δ18O values of seawater from the two locations, both measured and published. New data improve an existing calibration which was determined using measurements of salinity rather than directly measured δ18O values of the seawater and was composed of measurements from different species of sclerosponge and other aragonite-secreting organisms. The updated calibration (n = 12, r2 = 0.95) is: T(°C)=16.1(±3.1)-[6.5(±1.1)](δarag-δsw), where T is temperature in degrees Celsius, δarag is the δ18O value of aragonite normalized to VPDB, and δsw is the δ18O value of water normalized to VSMOW. This calibration improves accuracy and precision of Caribbean sclerosponges for reconstructions of temperature as well as δ18O values of seawater.