Re-evaluation of Sr/Ca ratio in coral skeletons as a proxy for temperature

Abstract

Components in biogenic carbonates have been recognized to be attractive tools for reconstructing past oceanographic and climatic changes. Although chemical components in coral aragonite are precipitated away from equilibrium, fluctuations of Sr/Ca ratio in coral skeletons have been empirically considered to be controlled by temperature. Thus, Sr/Ca ratio in coral skeletons has been applied for paleoclimate reconstruction. Recently, coupled measurements of coral skeletal δ¹⁸O, indicator of both SST and seawater δ¹⁸O, and Sr/Ca ratio are used to reconstruct seawater salinity as well as SST. On the other hand, it has been reported that Sr/Ca is also affected by growth rate of coral skeleton besides SST. However, the impact of skeletal growth rate on Sr/Ca ratio is a matter of debate and controversial results have been reported at the present. In this review, recent progress of studies on the topics and a mechanism of growth rate-related Sr/Ca variation based on a physiological model are summarized.