EVALUATION OF SAMPLING RESOLUTION IN CORAL STABLE-ISOTOPE RECORDS - ACASE-STUDY USING RECORDS FROM NEW-CALEDONIA AND TARAWA

We have generated a 40-year-long, monthly stable isotope record from a Porites lutea coral collected offshore of Amedee, New Caledonia (22 d egrees S, 167 degrees E) to investigate the relation between sampling resolution in coral isotope studies and retrieval of sea-surface envir onmental information. We interpret the high correlation between our ox ygen isotope record and a twenty-year long sea-surface temperature rec ord at the monthly timescale (r=0.88) to indicate that our coral isoto pe record is an accurate monitor of environmental conditions offshore of Amedee. The character of the signal and the percent variance explai ned in the record at the annual band, at the quasi-biennial oscillatio n band ((QBO) 2.0-2.4 years), and at the El Nino-Southern Oscillation band ((ENSO) 3-8 years) changes little in response to a reduction in s ampling density from monthly to bimonthly to quarterly. Similar result s have been obtained in a reanalysis of a coral isotope record from Ta rawa, Kiribati. Our results indicate that a significant amount of the information obtained from high-density sampling can also be retrieved from lower-density sampling. In particular, bimonthly sampling yields virtually no drop-off in variance explained, and quarterly sampling is satisfactory for resolving interannual and decadal-scale trends in ti me series. The proposed sampling approach may enable a more rapid fill ing in of numerous spatial holes in coral sampling sites needed for re construction of long-term decadal-scale variations in climate.