TWENTY YEARS OF WESTERN PACIFIC WARM POOL VARIABILITY AS RECORDED IN A PORITES CORAL FROM CHUUK LAGOON

The Western Pacific Warm Pool (WPWP) is a key aspect of the global climate, exchanging heat and carbon with the atmosphere as well as with the surrounding ocean and the underlying water masses. This region experiences large fluctuations in precipitation and temperature due to interannual oscillations in the El Niño – Southern Oscillation (ENSO). Chuuk Atoll (7°N, 152°E) is centrally located within the Warm Pool and provides an ideal location for studies of WPWP processes. Massive mounding corals have shown to be one of the best paleoclimate proxies, especially in warm, tropical regions because they have the powerful advantage of recording environmental changes in the seawater in which they are growing in their aragonitic skeletons. In addition, they grow relatively quickly in comparison to other marine calcifiers, providing the opportunity to make high-resolution (monthly or better) measurements. Determining the geochemical properties (δ¹⁸O, δ¹³C, Sr/Ca) of the calcium carbonate coral skeletons allows us to reconstruct past oceanic environmental conditions. Using the combination of stable isotope analyses and Sr/Ca measurements of the coral skeletal material, corals greatly contribute to a longer ocean observation record than is available through just the modern instrumental record.

Cores from large Porites lobata coral heads were collected from Chuuk Atoll in June 2011 and have undergone stable isotope (δ¹⁸O, δ¹³C) and trace element (Sr/Ca) analysis. The KIOST tropical marine station at Chuuk has been collecting temperature and salinity records for the past several years, making the calibration of geochemical data to temperature or salinity measurements much more accurate than simply using low-resolution model variables. Results covering the last 20 years indicate small annual temperature variations and large deviations in oxygen isotope values corresponding to El Niño years. Results will also be compared to a Porites coral core collected in 2008.