Stable isotopic evidence of El Nino-like atmospheric circulation in the Pliocene Western United States

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doi: 10.5194/cp-9-903-2013
Author(s): Winnick, M. J.; Welker, J. M.; Chamberlain, C. P.
Author Affiliation(s): Primary:
Stanford University, Environmental Earth System Science, Stanford, CA, United States
Other:
University of Alaska at Anchorage, United States
Volume Title: Climate of the Past
Source: Climate of the Past, 9(2), p.903-912. Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1814-9324
Note: In English. Includes supplement, http://www.clim-past.net/9/903/2013/cp-9-903-2013-supplement.zip; published in Climate of the Past Discussion, http://www.clim-past-discuss.net/8/5083/2012/cpd-8-5083-2012.html; accessed in July, 2013. 78 refs.; illus., incl. 1 table, sketch map
Summary: 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 Nino-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 Nino 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 Nino-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.
Year of Publication: 2013
Research Program: ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Arizona; Atmospheric circulation; Atmospheric precipitation; California; Cenozoic; Colorado; Detroit Seamount; Deuterium; East Pacific; El Nino; El Nino Southern Oscillation; Emperor Seamounts; Equatorial Pacific; Florida; Fluvial environment; Hydrogen; Idaho; Intertropical convergence zone; Isotope ratios; Isotopes; Kansas; Leg 138; Leg 145; Neogene; New Mexico; North Carolina; North Pacific; Northwest Pacific; O-18/O-16; ODP Site 846; ODP Site 882; Ocean Drilling Program; Oregon; Oxygen; Pacific Ocean; Paleoclimatology; Paleoenvironment; Paleosols; Paleotemperature; Pleistocene; Pliocene; Quaternary; Seasonal variations; South Pacific; Southeast Pacific; Stable isotopes; Tertiary; Texas; United States; Upper Quaternary; Utah; West Pacific
Coordinates: N502148 N502148 E1673600 E1673600
S030549 S030541 W0904904 W0904906
Record ID: 2014045644
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany