Details

Autor(en) / Beteiligte

• Fawcett, Peter J.
• Werne, Josef P.
• Anderson, R. Scott
• Heikoop, Jeffrey M.
• Brown, Erik T.
• Berke, Melissa A.
• Smith, Susan J.
• Goff, Fraser
• Donohoo-Hurley, Linda
• Cisneros-Dozal, Luz M.
• Schouten, Stefan
• Sinninghe Damsté, Jaap S.
• Huang, Yongsong
• Toney, Jaime
• Fessenden, Julianna
• WoldeGabriel, Giday
• Atudorei, Viorel
• Geissman, John W.
• Allen, Craig D.

Titel

Extended megadroughts in the southwestern United States during Pleistocene interglacials

Ist Teil von

• Nature (London), 2011-02, Vol.470 (7335), p.518-521

Ort / Verlag

London: Nature Publishing Group UK

Erscheinungsjahr

2011

Quelle

MEDLINE

Beschreibungen/Notizen

• A history of megadroughts Droughts lasting tens of years are known to have occurred in the southwestern United States during the past two millennia, but model simulations suggest that much longer 'megadroughts' might occur in a future, warmer climate. A new analysis of a lake sediment core from northern New Mexico reveals that such extreme droughts have occurred before: millennial-scale megadroughts were a regular feature of the warmest phases of Pleistocene interglacials. Mean annual temperatures during these droughts were comparable with or higher than today's. Comparison of the mid-Pleistocene climate record with that of the Holocene shows many similarities and suggests that were it not for anthropogenic warming, the southwestern United States would probably be entering a cool and wet phase by now. Droughts of tens of years are known to have occurred in the southwestern United States over the past two millennia, but model simulations suggest that much longer 'megadroughts' might occur in a future, warmer climate. So far, the presence of such droughts in the palaeoclimatic record has been unclear. Now, a lake sediment core from northern New Mexico is analysed, showing that millennial-scale megadroughts were a regular feature of Pleistocene interglacials. The results suggest that, in the absence of anthropogenic warming, the southwestern United States would probably be entering a cool and wet phase. 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 1 . Multi-year droughts during the instrumental period 2 and decadal-length droughts of the past two millennia 1 , 3 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 4 . 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 palaeotemperature proxies 5 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 C 4 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.