Intercolony δ18O and Sr/Ca variability among Porites spp. corals at Palmyra Atoll: Toward more robust coral‐based estimates of climate

Coral-based climate reconstructions at Palmyra Atoll face significant intercolony variability, with offsets in mean Sr/Ca and δ18O values introducing uncertainties of up to ±1.3 °C (1σ) for sea surface temperature (SST) estimates. Despite this, monthly to interannual variability in these proxies is consistent among colonies, suggesting that composite records from multiple corals can reduce reconstruction errors by 2.5 times—achieving a precision of ±0.6 °C (1σ). The study analyzed five Porites spp. coral cores spanning 1980–2010, revealing variability in proxy sensitivity to climate, with Sr/Ca-SST slopes ranging from −0.06 to −0.1 mmol mol⁻¹ °C⁻¹ and δ18O-SST slopes from −0.25 to −0.35‰ °C⁻¹. These findings underscore the need for multi-colony approaches to improve the robustness of coral-derived climate reconstructions in the tropical Pacific.

Sayani, H. R., Cobb, K. M., DeLong, K., Hitt, N. T., & Druffel, E. R. M. (2019). Intercolony δ¹⁸O and Sr/Ca variability among Porites spp. corals at Palmyra Atoll: Toward more robust coral‐based estimates of climate. Geochemistry, Geophysics, Geosystems, 20(11), 5270–5284. Portico. https://doi.org/10.1029/2019gc008420