The Sr/Ca-temperature relationship in coralline aragonite: Influence of variability in ( Sr/Ca) seawater and skeletal growth parameters

This paper provides an evaluation of two of the most likely pitfalls of Sr/Ca thermometry, i.e., the effect of biogenic cycling of Sr vs. Ca in the surface ocean and the effect of variable extension rate on Sr incorporation in coralline aragonite. We also report calibration of the Sr/Ca-temperature relationship for three coral species, Porites lobata, Pocillopora eydouxi and Pavona clavus, collected from the Hawaiian and Galapagos islands. Analyses of seawater samples show significant spatial and depth variability in the Sr:Ca ratio. The uncertainty introduced by this effect is estimated to be <0.2°C for corals located in tropical oligotrophic waters, and potentially larger for corals located in upwelling areas. Sr/Caanalyses along two different growth axes of a Galapagos Pavona clavus, with annual extension rates of ~6 and 12 mm/y, respectively, indicate an offset of 1-2°C, with higher Sr/Ca values associated with slower extension rates. The offset observed between the two growth axes may be the result of variations in extension and/or calcification rate.