Comparison of Imbrie-Kipp transfer function and modern analog temperature estimates using sediment trap and core top foraminiferal faunas

We evaluate the reliability of statistical estimates of sea surface temperature (SST) derived from planktonic foraminiferal faunas using the modern analog method and the Imbrie-Kipp method. Global core top faunas provide a calibration data set, while modern sediment trap faunas are used for validation. Linear regression of core top predicted SST against atlas SST generated slopes close to one for both methods. However, the Imbrie-Kipp transfer function temperature estimates had an intercept 1.3 degrees C warmer than modem analog estimates and 1.7 degrees C warmer than recorded atlas SST. The RMS error for the core top data set using the modern analog method (1.5 degrees C) was smaller than that of the Imbrie-Kipp method (1.9 degrees C). SST errors for the sediment trap faunas were not statistically different from those of the core top data set, regardless of method. Developing Imbrie-Kipp transfer functions for limited regions reduced the RMS variability but introduced residual structure not present in the global Imbrie-Kipp transfer function. Dissolution simulations with the sediment trap sample which generated the warmest SST residual for both methods suggests that the loss of delicate warm water foraminifera from midlatitude sediments may be the cause of this thermal error. We conclude that (1) the faunal structure of sediment trap and core top assemblages are similar; (2) both methods estimate SST reliably for modem foraminiferal flux assemblages, but the modern analog method exhibits less bias; and (3) both methods are relatively robust to samples with low communality but sensitive to selective faunal dissolution.