[OANNES Foro] Evolution and forcing mechanisms of El Niño over the past 21,000 years

[Mario Cabrejos]

Nature 515, 550–553

doi:10.1038/nature13963

Published online 26 November 2014

 

Evolution and forcing mechanisms of El Niño over the past 21,000 years

 
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
1> Zhengyu Liu1 2,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
2> Zhengyao Lu3,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
3> Xinyu Wen3,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
4> B. L. Otto-Bliesner4,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
5> A. Timmermann5 &
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#auth-
6> K. M. Cobb6

1Department of Atmospheric and Oceanic Sciences and Nelson Center for
Climatic Research, University of Wisconsin-Madison, Madison, Wisconsin
53706, USA

2Laboratory of Climate, Ocean and Atmosphere Studies, School of Physics,
Peking University, Beijing, 100871, China 3Climate and Global Dynamics
Division, National Center for Atmospheric Research, Boulder, Colorado
80307-3000, USA 4International Pacific Research Center and Department of
Oceanography, School of Ocean and Earth Science and Technology, University
of Hawaii at Manoa, Honolulu, Hawaii 96822, USA 5 School of Earth and
Atmospheric Sciences, Georgia 6 Institute of Technology, Atlanta, Georgia
30332, USA

 

·          

The El Niño Southern Oscillation (ENSO) is Earth’s dominant source of
interannual climate variability, but its response to global warming remains
highly uncertain
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref1>
1. To improve our understanding of ENSO’s sensitivity to external climate
forcing, it is paramount to determine its past behaviour by using
palaeoclimate data and model simulations. Palaeoclimate records show that
ENSO has varied considerably since the Last Glacial Maximum (21,000 years
ago)
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref2>
2,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref3>
3,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref4>
4,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref5>
5,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref6>
6,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref7>
7,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref8>
8,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref9>
9, and some data sets suggest a gradual intensification of ENSO over the
past ~6,000 years
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref2>
2,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref5>
5,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref7>
7,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref8>
8. Previous attempts to simulate the transient evolution of ENSO have relied
on simplified models
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref10
> 10 or snapshot
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref11
> 11,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref12
> 12,
<http://www.nature.com/nature/journal/v515/n7528/full/nature13963.html#ref13
> 13 experiments. Here we analyse a series of transient Coupled General
Circulation Model simulations forced by changes in greenhouse gasses,
orbital forcing, the meltwater discharge and the ice-sheet history
throughout the past 21,000 years. Consistent with most palaeo-ENSO
reconstructions, our model simulates an orbitally induced strengthening of
ENSO during the Holocene epoch, which is caused by increasing positive
ocean–atmosphere feedbacks. During the early deglaciation, ENSO
characteristics change drastically in response to meltwater discharges and
the resulting changes in the Atlantic Meridional Overturning Circulation and
equatorial annual cycle. Increasing deglacial atmospheric CO2 concentrations
tend to weaken ENSO, whereas retreating glacial ice sheets intensify ENSO.
The complex evolution of forcings and ENSO feedbacks and the uncertainties
in the reconstruction further highlight the challenge and opportunity for
constraining future ENSO responses.

 



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