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| Titel |
Implications of the permanent El Niño teleconnection "blueprint" for past global and North American hydroclimatology |
| VerfasserIn |
A. Goldner, M. Huber, N. Diffenbaugh, R. Caballero |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 7, no. 3 ; Nr. 7, no. 3 (2011-07-13), S.723-743 |
| Datensatznummer |
250004607
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| Publikation (Nr.) |
 copernicus.org/cp-7-723-2011.pdf |
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| Zusammenfassung |
| Substantial evidence exists for wetter-than-modern continental
conditions in North America during the pre-Quaternary warm climate intervals.
This is in apparent conflict with the robust global
prediction for future climate change of a northward
expansion of the subtropical dry zones that should drive aridification
of many semiarid regions. Indeed,
areas of expected future aridification include much of western North America,
where extensive paleoenvironmental records are documented
to have been much wetter before the onset of
Quaternary ice ages. It has also been proposed that climates previous to
the Quaternary may have been characterized as being in a state
with warmer-than-modern eastern equatorial sea surface temperatures
(SSTs). Because equatorial Pacific SSTs exert strong controls on
midlatitude atmospheric circulation and the global hydrologic cycle,
the teleconnected response from this permanent El Niño-like mean
state has been proposed as a useful analogue model, or "blueprint",
for understanding global climatological anomalies in
the past. The present study quantitatively explores the implications
of this blueprint for past climates with a specific focus on the
Miocene and Pliocene, using a global climate model
(CAM3.0) and a nested high-resolution climate model (RegCM3) to study the
hydrologic impacts on global and North American climate
of a change in mean SSTs resembling that which occurs during
modern El Niño events.
We find that the global circulation response to
a permanent El Niño resembles a large, long El Niño event.
This state also exhibits equatorial super-rotation, which
would represent a fundamental change to the tropical circulations. We
also find a southward shift in winter storm tracks
in the Pacific and Atlantic, which affects precipitation and temperature over the
mid-latitudes. In addition, summertime precipitation increases over the majority of the
continental United States. These increases in precipitation are controlled by
shifts in the subtropical jet and secondary atmospheric
feedbacks. Based on these results and the data proxy
comparison, we conclude that a permanent El Niño like state is one potential explanation of
wetter-than-modern conditions observed in paleoclimate-proxy records,
particularly over the western United States. |
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