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| Titel |
Stable isotopic evidence of El Niño-like atmospheric circulation in the Pliocene western United States |
| VerfasserIn |
M. J. Winnick, J. M. Welker, C. P. Chamberlain |
| 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 ; 9, no. 2 ; Nr. 9, no. 2 (2013-04-08), S.903-912 |
| Datensatznummer |
250018027
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| Publikation (Nr.) |
 copernicus.org/cp-9-903-2013.pdf |
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| Zusammenfassung |
| Understanding how the hydrologic cycle has responded to warmer global
temperatures in the past is especially important today as concentrations of
CO2 in the atmosphere continue to increase due to human activities. The
Pliocene offers an ideal window into a climate system that has equilibrated
with current atmospheric pCO2. During the Pliocene the western United
States was wetter than modern, an observation at odds with our current
understanding of future warming scenarios, which involve the expansion and
poleward migration of the subtropical dry zone. Here we compare Pliocene
oxygen isotope profiles of pedogenic carbonates across the western US to
modern isotopic anomalies in precipitation between phases of the El Niño–Southern Oscillation
(ENSO). We find that when accounting for seasonality of
carbonate formation, isotopic changes through the late Pliocene match modern
precipitation isotopic anomalies in El Niño years. Furthermore, isotopic
shifts through the late Pliocene mirror changes through the early
Pleistocene, which likely represents the southward migration of the westerly
storm track caused by growth of the Laurentide ice sheet. We propose that
the westerly storm track migrated northward through the late Pliocene with
the development of the modern cold tongue in the east equatorial Pacific,
then returned southward with widespread glaciation in the Northern
Hemisphere – a scenario supported by terrestrial climate proxies across the
US. Together these data support the proposed existence of background El
Niño-like conditions in western North America during the warm Pliocene.
If the earth behaves similarly with future warming, this observation has
important implications with regard to the amount and distribution of
precipitation in western North America. |
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