OPTIMAL SITES FOR CORAL-BASED RECONSTRUCTION OF GLOBAL SEA-SURFACE TEMPERATURE

We determine the structure of a network of sites from which coral-base d, proxy measurements of sea surface temperature (SST) variability min imize the error in a reconstruction of the large-scale features of the global SST field. For a wide range of coral-derived SST observational error and several minimization criteria, sites in the equatorial ocea ns, especially the central and eastern equatorial Pacific, best minimi ze the error in the reconstruction. If the observational error is suff iciently low, additional optimal sites are in selected subtropical lo, cations. If the observational error is high, the error is minimized by resampling the most important equatorial sites. The marginal return o n additional sites diminishes rapidly and is not sensitive to the size of the observational error: two sites reduce the analysis error by ha lf as much as 10 sites, while the first 6-7 sites achieve half the err or reduction of all 65 sites in the analysis domain. In the extratropi cs the reduction of reconstruction error is small and gradual, while e rror in the tropical Pacific is sharply reduced by 2-3 sites and gradu ally thereafter. These results suggest that a limited set of redundant ly sampled sites with uncorrelated and low observational error (approx imate to 0.3 degrees-0.6 degrees C) will provide the best approach to reconstruction of large-scale features of the SST field from coral dat a for the preinstrumental period.