Recent warming (2000-2010) and coral growth in the Western Pacific warm pool

Abstract

We investigated the oxygen isotopic variations in coral from Chuuk Atoll located in the Western Pacific Warm Pool (WPWP), with the goal to understand interannual variability of the WPWP and its influence on distant regions. Examination of X-ray images and stable oxygen isotopic values indicate that the coral records cover the period of the last 50 years approximately. The record of Pu activity also supports this age determination. The oxygen isotopic values of the coral skeleton illustrate the seasonal, interannual and decadal variability of sea surface condition which represent significant oceanographic changes of thermal and hydrologic variations in the region. For example, they were heavy for El Nino years and light values for La Nina years due to cool temperature and drier condition for El Nino period and warm temperature and increased precipitation for La Nina in the WPWP. Especially during the last 10 years (2000-2010) when the WPWP is characterized by a warming and freshening trend, the coral growth appears to be altered. X- ray images illustrate no distinctive annual band during these stressful years. Instead, micro layers are dominant. Coral skeletal density records also show light values for the period. We attribute the growth changes to environmental stress (warmer, fresher, possibly lower pH). In further studies we hope to identify these long-term environmental trends and their effects on the Chuuk Atoll corals.