Resolving Sea Level Changes during Previous Interglacials: best Practices from First Principles (Invited)

Inferred sea levels from previous interglacials are frequently derived from the elevations of U-Th dated fossil corals. The measurement accuracy of geodetic mapping and mass spectrometric dating methods has vastly improved over the last decade. However, resolving meter scale changes of sea level within an interglacial is challenging, and measurement techniques are no longer the dominant source of uncertainty. The obstacles to a robust and detailed sea level reconstruction are two-fold: 1) Corals grow at a range of depths below the sea surface, leading to uncertainty in the sea level elevation inferred from fossil corals. 2) Corals rarely remain a closed system for the radioisotopes used for dating, making it difficult to resolve the small differences in age required for a detailed sea level chronology. As a result, a typical fossil coral elevation versus age plot is a surprisingly poor guide to sea level history, and may be actually misleading in many cases. First principles suggest best practices for optimizing the chronology and resolution of interglacial sea level reconstructions.