Equatorial Pacific peak in biological production regulated by nutrient and upwelling during the late Pliocene/early Pleistocene cooling

[摘要] The largest increase in export production in the eastern Pacific of the last5.3 Myr (million years) occurred between 2.2 and 1.6 Myr, a time of majorclimatic and oceanographic reorganization in the region. Here, we investigatethe causes of this event using reconstructions of export production, nutrientsupply and oceanic conditions across the Pliocene–Pleistocene in the easternequatorial Pacific (EEP) for the last 3.2 Myr. Our results indicate that theexport production peak corresponds to a cold interval marked by high nutrientsupply relative to consumption, as revealed by the low bulk sedimentary¹⁵N/¹⁴N (δ¹⁵N) and alkenone-derived seasurface temperature (SST) values. This ∼0.6 million year long episodeof enhanced delivery of nutrients to the surface of the EEP was predominantlyinitiated through the upwelling of nutrient-enriched water sourced in highlatitudes. In addition, this phenomenon was likely promoted by the regionalintensification of upwelling in response to the development of intense Walkerand Hadley atmospheric circulations. Increased nutrient consumption in thepolar oceans and enhanced denitrification in the equatorial regionsrestrained nutrient supply and availability and terminated the high exportproduction event.

[学科分类] 地球化学与岩石