Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling
- 1Université Pierre et Marie Curie, UMR7159 LOCEAN, 4 Place Jussieu, 75252 Paris, France
- 2Graduate School of Oceanography, University of Rhode Island, Narragansett, RI 02882, USA
- 3Université Bordeaux 1, UMR5805 EPOC, avenue des facultés, 33405 Talence cedex, France
- 4Institut für Geowissenschaften, Christian-Albrechts-Universität Kiel, Ludewig-Meyn-Str. 10, 24118 Kiel, Germany
Abstract. The largest increase in export production in the eastern Pacific of the last 5.3 Myr (million years) occurred between 2.2 and 1.6 Myr, a time of major climatic and oceanographic reorganization in the region. Here, we investigate the causes of this event using reconstructions of export production, nutrient supply and oceanic conditions across the Pliocene–Pleistocene in the eastern equatorial Pacific (EEP) for the last 3.2 Myr. Our results indicate that the export production peak corresponds to a cold interval marked by high nutrient supply relative to consumption, as revealed by the low bulk sedimentary 15N/14N (δ15N) and alkenone-derived sea surface temperature (SST) values. This ∼0.6 million year long episode of enhanced delivery of nutrients to the surface of the EEP was predominantly initiated through the upwelling of nutrient-enriched water sourced in high latitudes. In addition, this phenomenon was likely promoted by the regional intensification of upwelling in response to the development of intense Walker and Hadley atmospheric circulations. Increased nutrient consumption in the polar oceans and enhanced denitrification in the equatorial regions restrained nutrient supply and availability and terminated the high export production event.