High-resolution productivity record and reconstruction of ENSO dynamics during the Holocene in the Eastern Equatorial Pacific using coccolithophores

Abstract

We provide high-resolution paleoproductivity data for the Holocene in the Eastern Equatorial Pacific (EEP). We describe the coccolithophore assemblages at Ocean Drilling Program (ODP) Site 1240 located in the Panama basin. Coccolithophore assemblages are proposed as a productivity proxy and nutricline position for the tropical Pacific Ocean. Our proxies can be used as a tool to reconstruct the El Niño-Southern Oscillation (ENSO), the main factor controlling the climate variability in the EEP. The equatorial upwelling intensity and the influence of waters with a Sub-Antarctic origin have controlled the productivity and the phytoplankton composition during the Holocene, and this has been strongly controlled by ENSO dynamics and, as our data suggest, by Southern Hemisphere ocean dynamics. Our results reveal a clear prevalence of dominant La Niña-like conditions during the early Holocene, with an intense upwelling and high primary productivity conditions in the EEP. La Niña-like conditions prevailed during the middle Holocene, although important fluctuations were observed in paleoproductivity, and some periods with a low primary productivity were recognizable (between 8.2 and 8 kyr and around 7 and 6.5 kyr), indicating a weakened upwelling stage, as occurs during El Niño events. A strong decrease in paleoproductivity occurred between 5 and 4.3 kyr, suggesting a relevant shift toward dominant El Niño-like conditions, with an increase in the stratification of the water column. An alternation between El Niño-like and La Niña-like dominant conditions occurred during the late Holocene, characterized by a clear trend toward prevailing El Niño-like conditions, with a low primary productivity.