Infra-sample, inter-sample and down-core microvariation in sea-surface temperature estimates obtained from planktonic foraminifera in the NE Atlantic

Abstract. Quantitative investigation of populations of planktonic foraminifera in core-top and down-core (top 10 cm) samples from 14 sites in the NE Atlantic, between 19° to 52°N and 11° to 30°W, have revealed no intra-sample, inter-sample or down-core variability beyond that to be expected on counts of 300 specimens (2 standard deviations, 95% confidence interval). Application of F20 transfer function analysis shows that estimates of sea-surface temperature, based on these counts, fall within a range of ±1.9°C (precision). However, when these estimates are compared with ‘actual’ temperatures within the 1° latitude/longitude squares containing the sites, the estimate errors range as high as ±3.6°C (accuracy). These results indicate there is a continuing need to improve methods for estimating proxy temperatures from planktonic foraminifera, in order to match the requirements of numerical modellers of past climates.