Eocene El Niño: evidence for robust tropical dynamics in the "hothouse"
Matthew Huber1, Rodrigo Caballero
1Danish Center for Earth System Science, Niels Bohr Institute for Astronomy, Physics, and Geophysics, University of Copenhagen, Juliane Maries Vej 30, DK-2100, Copenhagen Ø, Denmark. huberm@purdue.edu
Abstract:
Much uncertainty surrounds the interactions between the El Niño-Southern Oscillation (ENSO) and long-term global change. Past periods of extreme global warmth, exemplified by the Eocene (55 to 35 million years ago), provide a good testing ground for theories for this interaction. Here, we compare Eocene coupled climate model simulations with annually resolved variability records preserved in lake sediments. The simulations show Pacific deep-ocean and high-latitude surface warming of approximately 10 degrees C but little change in the tropical thermocline structure, atmosphere-ocean dynamics, and ENSO, in agreement with proxies. This result contrasts with theories linking past and future "hothouse" climates with a shift toward a permanent El Niño-like state.
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