Eocene El Niño: Evidence for Robust Tropical Dynamics in the "Hothouse"
Matthew Huber,*
Rodrigo Caballero
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 ~10°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.
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.
*
Present address: Earth and Atmospheric Sciences Department, 1397 Engineering Building, West Lafayette, IN 47907, USA.
To whom correspondence should be addressed. E-mail:
huberm{at}purdue.edu
