Precise determination of Sr/Ca by laser ablation ICP-MS compared to ICP-AES and application to multi-century temperate corals

Coral skeletal Sr/Ca compositions are valuable tools for the reconstruction of past tropical climate. While solution-based ICP-AES has become the preferred method to obtain monthly-resolved Sr/Ca records as proxy for sea-surface temperature (SST), laser ablation ICP-MS (LA-ICP-MS) allows a more rapid and still precise analysis of multiple elemental ratios at higher spatial resolution and, measurements can easily be replicated. However, the methodology still needs to be refined for long corals. It is applied here to a 435 year old Porites coral from the temperate region of southern Japan. Sr/Ca ratios measured by LA-ICP-MS and ICP-AES for three 10-15 yr periods are shown to be highly consistent. Resolution, data processing and Sr/Ca-SST calibration issues are discussed, and a replicate strategy is proposed to ensure high-precision Sr/Ca records from multi-century corals using LA-ICP-MS.