abstract:Faunal indices of sea-surface temperature (SST) have been widely used for reconstructing past ocean variability and for verifying the results of climate modeling. Recent studies on the distribution patterns of modern planktonic foraminifers on surface sediments have indicated important relationships with many hydrographic variables associated with the vertical structure of upper-layer oceans. To investigate whether these other ocean hydrographic variables are important to the changes in the faunal distribution pattern, two sets of core-top faunal data from modern low-latitude Pacific surface sediments were compiled to compare with direct observations of SST as well as the depth of thermocline (DOT), a primarily important variable for describing the vertical structure of upper-layer oceans at low latitudes. The degree of correlation between the faunal principal components, defined by a Q-mode principal component analysis, SST, DOT, and a carbonate preservation index (CPI), was examined using simple and partial correlation analyses. This study indicates that the effect of DOT controls on faunal distributions of planktonic foraminifers in the low-latitude Pacific is important and interpreting the DOT or other hydrographic variables of upper-layer oceans from planktonic foraminifer faunal data would be more appropriate in future paleoceanographic applications.