Upwelling intensification as part of the Pliocene-Pleistocene climate transition.

A deep-sea sediment core underlying the Benguela upwelling system off southwest Africa provides a continuous time series of sea surface temperature (SST) for the past 4.5 million years. Our results indicate that temperatures in the region have declined by about 10 degrees C since 3.2 million years ago. Records of paleoproductivity suggest that this cooling was associated with an increase in wind-driven upwelling tied to a shift from relatively stable global warmth during the mid-Pliocene to the high-amplitude glacial-interglacial cycles of the late Quaternary. These observations imply that Atlantic Ocean surface water circulation was radically different during the mid-Pliocene.