Steph, Silke, Tiedemann, Ralf, Groeneveld, Jeroen, Sturm, Arne and Nürnberg, Dirk (2006) Pliocene changes in tropical east Pacific upper ocean stratification: response to tropical gateways?. Proceedings of the Ocean Drilling Program: Scientific Results, 202 . pp. 1-51. DOI 10.2973/odp.proc.sr.202.211.2006.

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Abstract

A combination of stable isotope records and Mg/Ca temperature estimates of four different planktonic foraminiferal species from Ocean Drilling Program Site 1241 allows differentiation between temperature and salinity changes in the tropical east Pacific (TEP) upper water column during the Pliocene (~5.7–2.1 Ma). The deviation of δ18O records and Mg/Ca temperature estimates from thermocline-dwelling planktonic foraminifers suggests that local changes in salinity exerted a much stronger control on Pliocene TEP upper ocean water mass signatures than previously assumed. The most pronounced Pliocene change
in TEP upper ocean stratification was the shoaling of the thermocline from ~4.8 to 4.0 Ma that was possibly triggered by changes in the configuration of low-latitude ocean gateways. During this time interval, mixed-layer temperatures and salinities remained relatively constant in
contrast to a pronounced temperature (~6°C) and salinity decrease at the bottom of the photic zone. This change led to a new state in the thermal structure of the TEP, as the thermocline remained relatively shallow until ~2.1 Ma.

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