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Extended megadroughts in the southwestern United States during Pleistocene interglacials

机译:更新世间冰期期间美国西南部的大干旱

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摘要

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' mega-drought 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 proxies5 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 ℃ 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 ℃) 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.
机译:在美国西南半干旱地区,与人为气候变化相关的干旱频率和严重程度增加的潜力令人严重关注。据预测,仪器期的多年干旱和过去两千年的年代际干旱较短,而且在气候上与未来数十年至一个世纪的永久性“粉碗状”特大干旱条件(持续数十年至一个世纪)不同。变暖的结果。到目前为止,尚不清楚在美国西南部是否发生过这种大旱灾,如果发生这种大旱灾,其规律性和强度是什么。在这里,我们表明,干旱时期持续了几个世纪至几千年,发生在美国西南部的中更新世间冰期。利用分子古温度代理5重建新墨西哥州Valles火山口的更新世中相湖相沉积物的年平均温度(MAT),我们发现最干燥的条件发生在冰间期最热的阶段,当MAT与比现代MAT高。在这些温暖,干燥的间隔中,耐旱的C_4植物群落的崩溃表明夏季降水显着减少,这可能是由于亚热带干旱区的极地迁移所致。在海洋同位素阶段(MIS)11内发生了三个振幅〜2℃的MAT周期,它们似乎与该冰间期的静音进动周期相对应。与MIS 11相比,MIS 13的进动周期振幅更大,MAT的变化较大(4-6℃),并且持续的温暖期更长,这表明局部日照变化对美国西南部的冰间气候变化很重要。 MIS 11早期气候记录与全新世记录的比较显示出许多相似之处,这意味着在没有人为强迫的情况下,该地区应该进入凉爽湿润的时期。

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  • 来源
    《Nature》 |2011年第7335期|p.518-521|共4页
  • 作者单位

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Large Lakes Observatory and Department of Chemistry and Biochemistry, University ofMinnesota Duluth, Duluth, Minnesota 55812, USA,Centre for WaterResearch, University of Western Australia, Crawley, Western Australia 6009, Australia,WA-Organic and Isotope Geochemistry Centre, Curtin University of Technology, Bentley, Western Australia 6845,Australia;

    School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona 86011, USA,Iaboratory of Paleoecology, Bilby Research Center, Northern ArizonaUniversity, Flagstaff, Arizona 86011, USA;

    Earth and Environmental Sciences Division, EES-14, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA;

    Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, Minnesota 55812, USA;

    Large Lakes Observatory and Department of Geological Sciences, University of Minnesota Duluth, Duluth, Minnesota 55812, USA;

    Iaboratory of Paleoecology, Bilby Research Center, Northern ArizonaUniversity, Flagstaff, Arizona 86011, USA;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Earth and Environmental Sciences Division, EES-14, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA;

    NI0Z Royal Netherlands Institute forSea Research, Department of Marine Organic Biogeochemistry, PO Box 59,1790 AB Den Burg, Netherlands;

    NI0Z Royal Netherlands Institute forSea Research, Department of Marine Organic Biogeochemistry, PO Box 59,1790 AB Den Burg, Netherlands;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Earth and Environmental Sciences Division, EES-14, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA;

    School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona 86011, USA;

    School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, Arizona 86011, USA;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

    Department of Earth & Planetary Sciences, University of New Mexico, Albuquerque, New Mexico 87131, USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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