Characterizing seawater oxygen isotopic variability in a regional ocean modeling framework: Implications for coral proxy records

A major impact of downscaling at the Line Islands is the ability to resolve fronts associated with tropical instability waves (TIWs), which generate large excursions in both temperature and seawater δ¹⁸O at Palmyra Atoll (5.9°N, 162.1°W). TIW-related sea surface temperature gradients are smaller at neighboring Christmas Island (1.9°N, 157.5°W), but the interaction of mesoscale features with the steep island topography nonetheless generates cross-island temperature differences of up to 1°C. These nonlinear processes alter the slope of the salinity:seawater δ¹⁸O relationship at Palmyra and Christmas, as well as affect the relation between coral δ¹⁸O and indices of ENSO variability.

Consideration of the full physical oceanographic context of reef environments is therefore crucial for improving δ¹⁸O-based ENSO reconstructions.