NOAA/WDS Paleoclimatology - Eastern Equatorial Pacific d18O and d13C Data from the Last Glacial Maximum

The mean state and variability of the tropical Pacific is influenced by the depth of the thermocline. During the Last Glacial Maximum (~21,000 years ago), the zonal sea surface temperature gradient across the equatorial Pacific was reduced and productivity was generally lower than modern. To understand the thermocline depth's role in determining the Last Glacial Maximum tropical mean state, we reconstruct the upper ocean d18O profile from multiple species of planktic foraminifera. We synthesize existing records of surface and subsurface dwelling foraminifera to reconstruct the vertical d18O gradient throughout the eastern equatorial Pacific. We find the thermocline was deeper during the Last Glacial Maximum than the Holocene throughout the eastern equatorial Pacific region. The thermocline depth's role in the dynamic forcing of the cold tongue contributed to the reduced zonal SST gradient across the equatorial Pacific, decreased productivity, and presumably impacted El Niño-Southern Oscillation variability relative to the Holocene.