Eocene El Niño: evidence for robust tropical dynamics in the "hothouse".
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.
Huber
Matthew
M
Danish 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
Caballero
Rodrigo
R