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.
We present a new high-resolution reconstruction of annual sea-surface temperatures (SSTa) and net primary productivity (NPP) using novel coccolithophore-based models developed for the Eastern Equatorial Pacific (EEP). We combined published coccolithophore census counts from core-tops in the Eastern Pacific with 32 new samples from the Equatorial region, to derive a new statistical model to reconstruct SSTa. Results show that the addition of the new EEP samples improves existing coccolithophore-based SST-calibrations, and allow reconstructing SSTa in the EEP with higher confidence. We also merged the relative abundance of deep-photic species Florisphaera profunda in the same surface sediment samples with existing calibration datasets for tropical regions, to reconstruct annual NPP. Both temperature and productivity calibrations were successfully applied to fossil coccolith data from Ocean Drilling Project Site 1240, in the EEP. The coccolith-based SSTa estimates show a cooling during the Last Glacial Maximum (LGM) and the Younger Dryas, and warming at the start of the Holocene. This pattern differs in the timing and magnitude of the temperature changes from other available SST-reconstructions based on biogeochemical and faunal proxies. We discuss these discrepancies to be the result of different proxy sensitivities to insolation forcing, seasonal bias, and/or preservation artifacts. Reconstructed annual NPP shows a general decreasing trend from the late last glacial period to recent times, which we relate to the weakening of wind-driven equatorial upwelling towards the Holocene. We also calculated carbon export using our SSTa and NPP reconstructions, and compared to other geochemical-based reconstructions for the same location. Our coupled SSTa-NPP reconstruction provides key data to more fully assess the evolution of primary and export productivity as well as organic carbon burial in the EEP, with implications for its role in global biogeochemical cycles across glacial terminations.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.