A coral record from the West Pacific Warm Pool (New Georgia)

The Western Pacific Warm Pool (WPWP) acts as the heat engine for Earth¡_s climate and as a major moisture source for the global hydrological cycle. There is a long-standing uncertainty about the stability of SST changes in this key region. Here we use elemental ratio (Sr/Ca) and oxygen isotope data from a Porites coral head collected offshore Gizo Island, New Georgia (8° S, 155° E), a site that is located in the warmest part of the WPWP, to assess the degree to which changes in these geochemical variables reflect variations in sea surface conditions. Contrary to other regions, the Sr/Ca and SST relation is unimpressive in the raw data (r= -0.4). Removal of a PDO (Pacific Decadal Oscillation) signal improves the correlation (r= -0.67), but it is still less than the normal Sr/SST correlation. The correlation between ENSO filtered Sr/Ca and SST also shows decadal variations, following the phase shift of PDO index. It is generally highly correlated when ¡°warm¡± PDO regimes dominated ( ∣ r∣ = 0.74 ∼ 0.88), and poorly correlated when ¡°cool¡± PDO regimes prevailed ( ∣ r∣ ≤ 0.3). We therefore used cyclostationary EOFs to develop a transfer function to isolate the annual cycle in the Sr/Ca record and get a much more reliable estimate of SST (r= 0.86, from 1932 to 1964). A prediction of the linear growth rate curve suggests that the bottom of the core is ∼ 1706, thus this may be the first coral record with the potential of extracting a Little Ice Age signal from the WPWP.