Super ENSO and Global Climate Oscillations at Millennial Time Scales

Abstract

The late Pleistocene history of seawater temperature and salinity variability in the western tropical Pacific warm pool is reconstructed from oxygen isotope (δ 18 O) and magnesium/calcium composition of planktonic foraminifera. Differentiating the calcite δ 18 O record into components of temperature and local water δ 18 O reveals a dominant salinity signal that varied in accord with Dansgaard/Oeschger cycles over Greenland. Salinities were higher at times of high-latitude cooling and were lower during interstadials. The pattern and magnitude of the salinity variations imply shifts in the tropical Pacific ocean/atmosphere system analogous to modern El Niño–Southern Oscillation (ENSO). El Niño conditions correlate with stadials at high latitudes, whereas La Niña conditions correlate with interstadials. Millennial-scale shifts in atmospheric convection away from the western tropical Pacific may explain many paleo-observations, including lower atmospheric CO 2 , N 2 O, and CH 4 during stadials and patterns of extratropical ocean variability that have tropical source functions that are negatively correlated with El Niño.