Investigating ENSO‐Related Temperature Variability in Equatorial Pacific Core‐Tops Using Mg/Ca in Individual Planktic Foraminifera

Abstract

AbstractEl Niño Southern Oscillation (ENSO) is the largest source of interannual climate variability on Earth today; however, future ENSO remains difficult to predict. Evaluation of paleo‐ENSO may help improve our basic understanding of the phenomenon and help resolve discrepancies among models tasked with simulating future climate. Individual foraminifera analysis allows continuous down‐core records of ENSO‐related temperature variability through the construction and comparison of paleotemperature distributions; however, there has been little focus on calibrating this technique to modern conditions. Here, we present data from individual measurements of Mg/Ca in two species of planktic foraminifera, surface dwelling Globigerinoides ruber and thermocline dwelling Neogloboquadrina dutertrei, from nine core tops across the equatorial Pacific (n ≈ 70 per core for each species). Population variance, kernel probability density functions, and quantile‐quantile analyses are used to evaluate the shape of each Mg/Ca‐temperature distribution and to compare them to modern conditions using monthly temperatures from the Simple Ocean Data Assimilation. We show that populations of individual Mg/Ca measurements in both G. ruber and N. dutertrei reflect site‐specific temperature distribution shapes and variances across the equatorial Pacific when accounting for regional differences in depth habitats. Individual measurements of both taxa capture zonal increases in population variance from the western equatorial Pacific to the central equatorial Pacific and a spatially heterogeneous eastern equatorial Pacific, consistent with modern conditions. Lastly, we show that populations of individual Mg/Ca measurements are able to recover meaningful differences in temperature variability between sites within the eastern equatorial Pacific, lending support to this tool's application for paleo‐ENSO reconstructions.