SEA SURFACE TEMPERATURE FIELD RECONSTRUCTION FROM CORAL DATA: METHODOLOGY AND APPLICATION (EL NINO SOUTHERN OSCILLATION).

다국어 초록 (Multilingual Abstract)

A primary objective of paleoclimate research is the characterization of natural climate variability on time scales of years to millennia. The goal of this thesis is the systematic, objective, and verifiable reconstruction of the sea surface temperature (SST) field from coral δ₁₈O data, using reduced space objective analysis. In this approach we seek to reconstruct only the leading modes of large-scale SST variability from a sparse observational network. The development of a proxy record of SST from the central equatorial Pacific and solution of the observational array design problem for coral data suggest that a few well-located sampling sites may be sufficient to resolve the leading modes of global SST variability. Cross-validation of available coral δ<super>18</super>O data and historical SST analyses indicate that three modes of variability may be reconstructed. These are the oceanographic signatures of the El NiNo-Southern Oscillation (ENSO), a global warming trend in which the eastern equatorial Pacific cools, and an ENSO-like Pacific decadal pattern. These modes are reconstructed for the 1607–1992 period using the coral data. Verification exercises indicate the reconstruction is useful back to about 1800. Analysis of the NINO3 SST index computed for the reconstruction suggests that ENSO frequency in the early 1800s was similar to that observed in the late 1800s and in the last few decades. Additional longer coral time series will improve the resolution of these large-scale SST modes, given that the observations are unbiased and appropriate observational errors have been prescribed.