Latest Pleistocene to Holocene hydroclimates from Lake Elsinore, California
Latest Pleistocene to Holocene hydroclimates from Lake Elsinore, California
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DOI：
10.1016/j.quascirev.2013.05.023
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发表时间：
2013-09
影响因子：
4
通讯作者：
M. Kirby;S. Feakins;Nicole Bonuso;Joanna M. Fantozzi;C. Hiner
中科院分区：
文献类型：
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作者：
M. Kirby;S. Feakins;Nicole Bonuso;Joanna M. Fantozzi;C. Hiner
美国西南部地区的水文气候在更新世末期突然发生变化，北美大陆冰盖从最南端退缩。为了调查这种变化的性质，我们提出了一个新的记录，从埃尔西诺湖，位于内陆36公里，从太平洋南部加州和评估它的背景下，在整个沿海和内陆的美国西南部，包括墨西哥西北部的记录。从埃尔西诺湖获得的沉积物岩心提供了一个连续的序列，具有19-9 ka BP的多年代际分辨率。沉积学和地球化学分析揭示了水文变异性。特别是，砂和碳酸盐成分表明在最古老的Dryas（OD），Bølling-Allerød（BA）和新Dryas（YD）过渡的突然变化，与格陵兰岛的时间一致。对植物叶蜡中C28正链烷酸的氢同位素分析（δDwax）显示，在19 - 9 ka BP期间，δ Dwax值呈现出负值减小的长期趋势。OD期间的δ Dwax值表明，降水来自北太平洋的水汽源，这与倾斜西风带假说一致。我们没有发现北美季风的同位素证据，远至西部的埃尔西诺湖，因此，我们推断，湿/干的变化在西南沿海地区表示，通过冬季降水，符合现代气候学。比较埃尔西诺湖其他西南记录（特别是钟洞和斯坦顿堡），我们发现一致的时间的主要过渡（OD BA，BA到YD）和水文响应在OD和BA。水文响应，但是，在YD一致的偶极子之间的沿海和西南内陆变化。在OD（湿），BA（干燥）和YD（湿）期间，美国西南部和墨西哥西北部内陆的水文响应的连贯模式遵循大西洋经向翻转环流的变化，可能是通过其对北太平洋冬季风暴路径和北美季风的范围/幅度的综合影响。相比之下，埃尔西诺湖和西南沿海经历了冰消期的干旱趋势，在OD到BA和BA到YD的过渡期突然变化。这一趋势跟踪温室气体上升通过冰川消退，与一个明显的南移西风水分来源调整冰盖退缩。
The hydroclimate of the southwestern United States (US) region changed abruptly during the latest Pleistocene as the continental ice sheets over North America retreated from their most southerly extent. To investigate the nature of this change, we present a new record from Lake Elsinore, located 36 km inland from the Pacific Ocean in Southern California and evaluate it in the context of records across the coastal and interior southwest United States, including northwest Mexico. The sediment core recovered from Lake Elsinore provides a continuous sequence with multi-decadal resolution spanning 19–9 ka BP. Sedimentological and geochemical analyses reveal hydrologic variability. In particular, sand and carbonate components indicate abrupt changes at the Oldest Dryas (OD), Bølling–Allerød (BA), and Younger Dryas (YD) transitions, consistent with the timing in Greenland. Hydrogen isotope analyses of the C28n-alkanoic acids from plant leaf waxes (δDwax) reveal a long term trend toward less negative values across 19−9 ka BP.δDwaxvalues during the OD suggest a North Pacific moisture source for precipitation, consistent with the dipping westerlies hypothesis. We find no isotopic evidence for the North American Monsoon reaching as far west as Lake Elsinore; therefore, we infer that wet/dry changes in the coastal southwest were expressed through winter-season precipitation, consistent with modern climatology. Comparing Lake Elsinore to other southwest records (notably Cave of Bells and Fort Stanton) we find coincident timing of the major transitions (OD to BA, BA to YD) and hydrologic responses during the OD and BA. The hydrologic response, however, varied during the YD consistent with a dipole between the coastal and interior southwest. The coherent pattern of hydrologic responses across the interior southwest US and northwest Mexico during the OD (wet), the BA (drier), and YD (wet) follows changes in the Atlantic Meridional Overturning Circulation, presumably via its combined influence on North Pacific winter storm tracks and the extent/magnitude of the North American Monsoon. In contrast, Lake Elsinore and the coastal southwest experiences a deglacial drying trend punctuated by abrupt change at the OD to BA and BA to YD transitions. This trend tracks rising greenhouse gases through the deglacial, with an apparent southward shift in westerly moisture sources adjusting to the retreating ice sheet.