Evolution of the zonal gradients across the equatorial Pacific during the Miocene–Pleistocene

Catherine Beltran (1) , Gabrielle Rousselle (1) , Marc de Rafélis (2) , Marie-Alexandrine Sicre (3) , Nathalie Labourdette (1) , Stefan Schouten (4)

1 iSTeP - Institut des Sciences de la Terre de Paris
2 GET - Géosciences Environnement Toulouse
3 VOG - Variabilité de l'Océan et de la Glace de mer
4 Department of Marine Biogeochemistry and Toxicology

Combining U^k'₃₇ -and TEX₈₆-derived temperatures and oxygen isotopic values of mixed-layer and thermocline species from the IODP site U1338 (East Equatorial Pacific) and ODP Site 806 (West Equatorial Pacific) we assess the evolution of the zonal sea-surface temperature gradients and thermocline depth across the equatorial Pacific from the late Miocene through the Pleistocene. Data suggest a long-term shoaling of the thermocline along the equator throughout the Miocene-Pliocene that accelerated around 5.3 Ma. We identify a critical transition at about 3.8 Ma from a El-Niño-like-dominated mean state during the late Miocene and early Pliocene to a La-Niña-like-dominated state during the late Pliocene-Pleistocene. This transition coincides with the restriction of the Indonesian seaway and the onset of ice growth in the northern hemisphere and in Antarctica that led to the long-term strengthening of the Walker circulation and affected low-latitude zonal gradient.

Keywords: Equatorial Pacific; Miocene Pliocene climate; biomarker proxies; planktonic foraminifera; coccoliths

Domains: Climatology; Ocean, Atmosphere

Catherine Beltran, Gabrielle Rousselle, Marc de Rafélis, Marie-Alexandrine Sicre, Nathalie Labourdette, et al.. Evolution of the zonal gradients across the equatorial Pacific during the Miocene–Pleistocene. Journal of Sedimentary Research, 2019, 89 (3), pp.242-252. ⟨10.2110/jsr.2019.15⟩. ⟨insu-02104911⟩