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The evolution of the equatorial thermocline and the early Pliocene El Padre mean state
Author(s) -
Ford Heather L.,
Ravelo A. Christina,
Dekens Petra S.,
LaRiviere Jonathan P.,
Wara Michael W.
Publication year - 2015
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2015gl064215
Subject(s) - thermocline , geology , oceanography , structural basin , climatology , sea surface temperature , paleontology
The tropical Pacific thermocline strength, depth, and tilt are critical to tropical mean state and variability. During the early Pliocene (~3.5 to 4.5 Ma), the Eastern Equatorial Pacific (EEP) thermocline was deeper and the cold tongue was warmer than today, which resulted in a mean state with a reduced zonal sea surface temperature gradient or El Padre . However, it is unclear whether the deep thermocline was a local feature of the EEP or a basin‐wide condition with global implications. Our measurements of Mg/Ca of Globorotalia tumida in a western equatorial Pacific site indicate Pliocene subsurface temperatures warmer than today; thus, El Padre included a basin‐wide thermocline that was relatively warm, deep, and weakly tilted. At ~4 Ma, thermocline steepening was coupled to cooling of the cold tongue. Since ~4 Ma, the basin‐wide thermocline cooled/shoaled gradually, with implications for thermocline feedbacks in tropical dynamics and the interpretation of TEX 86 ‐derived temperatures.