NOAA/WDS Paleoclimatology - Eastern Equatorial Pacific 150KYr d15N and Corg Data

High-resolution downcore records of bulk sediment nitrogen isotopes (d15N) and organic carbon (Corg) contents from multiple Eastern Tropical Pacific sites show remarkable uniformity during the last glacial stage, whereas during the Holocene and the last interglacial period, they diverge significantly. The close covariation of d15N records during glacial stages points toward regional changes in the background isotopic signal of the inorganic nitrate pool, likely caused by variations in the denitrification rates in the nearby suboxic zones. On the other hand, we attribute the divergence of the d15N and Corg records during interglacial periods to a spatial reorganization in the equatorial divergence. We posit a southward displacement of the zone of strongest upwelling in the South Equatorial Current to explain the reduced productivity and higher nitrate consumption recorded at the equator during warmer intervals.