Stable isotope ratios on foraminifera from Site 138-846, supplement to: Scroxton, Nick; Bonham, Sarah G; Rickaby, Rosalind E M; Lawrence, Sophie H F; Hermoso, Michael; Haywood, Alan M (2011): Persistent El Niño-Southern Oscillation variation during the Pliocene Epoch. Paleoceanography, 26, PA2215, 13 pp

• Main Authors: Scroxton, Nick, Bonham, Sarah G, Rickaby, Rosalind E M, Lawrence, Sophie H F, Hermoso, Michael, Haywood, Alan M
• Format: Dataset
• Language: English
• Published: PANGAEA - Data Publisher for Earth & Environmental Science 2011
• Subjects: Sample code/label; DEPTH, sediment/rock; AGE; Sample ID; Sea surface temperature; Neogloboquadrina dutertrei, δ18O; Neogloboquadrina dutertrei, δ13C; Mass; Globigerinoides ruber, δ18O; Globigerinoides ruber, δ13C; Globorotalia menardii, δ18O; Globorotalia menardii, δ13C; Drilling/drill rig; DSDP/ODP/IODP sample designation; SST calculated from alkenones; Leg138; Joides Resolution; Ocean Drilling Program ODP; Pacific; Planktonic foraminifera
• Online Access: https://dx.doi.org/10.1594/pangaea.744735; https://doi.pangaea.de/10.1594/PANGAEA.744735

There is an urgent requirement to understand how large fluctuations in tropical heat distribution associated with the El Niño-Southern Oscillation (ENSO) will respond to anthropogenic emissions of greenhouse gases. Intervals of global warmth in Earth history provide a unique natural laboratory to explore the behaviour of the ENSO in a warmer world. To investigate interannual climatic variability, specifically ENSO, in the mid-Piacenzian Warm Period (mPWP: 3.26 - 3.03 Ma), we integrate observations from the stable isotopes of multiple individual planktonic foraminifera from three different species from the eastern equatorial Pacific (EEP) with ENSO simulations from HadCM3, a fully coupled ocean-atmosphere climate model. Our proxy data and model outputs show persistent inter-annual variability during the mPWP caused by a fluctuating thermocline, despite a deeper thermocline and reduced upwelling. We show that the likely cause of the deeper thermocline is due to warmer equatorial undercurrents rather than reduced physical upwelling. We conclude that the mPWP was characterized by ENSO related variability around a mean state akin to a modern El Niño event. Furthermore, HadCM3 predicts that the warmer Pliocene world is characterized by a more periodic, regular amplitude ENSO fluctuation, suggestive that the larger and deeper west Pacific warm pool is more easily destabilized eastwards. These conclusions are comparable to the observed trend over the last forty years to more regular and intense ENSO events. Future research must resolve whether global warming alone, or in concert with tectonic factors, was sufficient to alter ENSO variability during warm intervals of the Pliocene.