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Extended megadroughts in the southwestern United States during Pleistocene interglacials

Valles Caldera, US NPS image
Valles Caldera. US NPS image
Extended megadroughts in the southwestern United States during Pleistocene interglacials

Vol. 470, pp. 518-521, 24 February 2011
DOI: 10.1038/nature09839

Peter J. Fawcett1, Josef P. Werne2,4,5, R. Scott Anderson6,7, Jeffrey M. Heikoop8, Erik T. Brown3, Melissa A. Berke3, Susan J. Smith7, Fraser Goff1, Linda Donohoo-Hurley1, Luz M. Cisneros-Dozal8, Stefan Schouten9, Jaap S. Sinninghe Damsté9, Yongsong Huang10, Jaime Toney8, Julianna Fessenden6, GidayWoldeGabriel6, Viorel Atudorei1, John W. Geissman1 & Craig D. Allen11
The potential for increased drought frequency and severity linked to anthropogenic climate change in the semi-arid regions of the southwestern United States (US) is a serious concern. Multi-year droughts during the instrumental period and decadal-length droughts of the past two millennia were shorter and climatically different from the future permanent, 'dust-bowl-like' megadrought conditions, lasting decades to a century, that are predicted as a consequence of warming. So far, it has been unclear whether or not such megadroughts occurred in the southwestern US, and, if so, with what regularity and intensity. Here we show that periods of aridity lasting centuries to millennia occurred in the southwestern US during mid-Pleistocene interglacials. Using molecular palaeo- temperature proxies to reconstruct the mean annual temperature (MAT) in mid-Pleistocene lacustrine sediment from the Valles Caldera, New Mexico, we found that the driest conditions occurred during the warmest phases of interglacials, when the MAT was comparable to or higher than the modern MAT. A collapse of drought-tolerant C4 plant communities during these warm, dry intervals indicates a significant reduction in summer precipitation, possibly in response to a poleward migration of the subtropical dry zone. Three MAT cycles ~2°C in amplitude occurred within Marine Isotope Stage (MIS) 11 and seem to correspond to the muted precessional cycles within this interglacial. In comparison with MIS 11, MIS 13 experienced higher precessional-cycle amplitudes, larger variations in MAT (4-6°C) and a longer period of extended warmth, suggesting that local insolation variations were important to interglacial climatic variability in the southwestern US. Comparison of the early MIS 11 climate record with the Holocene record shows many similarities and implies that, in the absence of anthropogenic forcing, the region should be entering a cooler and wetter phase.
Download data from the WDC Paleo archive:
Valles Caldera Pleistocene Interglacial Multiproxy Sediment Data, Text or Excel

To read or view the full study, please visit the Nature website.
It was published in Nature, Vol. 470, pp. 518-521, 24 February 2011 DOI: 10.1038/nature09839
1 Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA.
2 Large Lakes Observatory and Department of Chemistry and Biochemistry, University of Minnesota Duluth, Duluth, Minnesota 55812, USA.
3 Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, Minnesota 55812, USA
4 Centre for Water Research, University of Western Australia, Crawley, Western Australia 6009, Australia.
5 WA-Organic and Isotope Geochemistry Centre, Curtin University of Technology, Bentley, Western Australia 6845, Australia.
6 School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona 86011, USA
7 Laboratory of Paleoecology, Bilby Research Center, Northern Arizona University, Flagstaff, Arizona 86011, USA.
8 Earth and Environmental Sciences Division, EES-14, Los Alamos National Laboratory, Los Alamos,NewMexico 87545, USA
9 NIOZ Royal Netherlands Institute for Sea Research, Department of Marine Organic Biogeochemistry, PO Box 59, 1790 AB Den Burg, Netherlands
10 Department of Geological Sciences, Brown University, Providence, Rhode Island 02912, USA
11 USGS Fort Collins Science Center, Jemez Mountains Field Station, Los Alamos, New Mexico 87544, USA.
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