Precipitation changes over the eastern Bolivian Andes inferred from speleothem (δ18O) records for the last 1400 years
Precipitation changes over the eastern Bolivian Andes inferred from speleothem (δ18O) records for the last 1400 years
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DOI：
10.1016/j.epsl.2018.04.048
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发表时间：
2018-07-15
影响因子：
5.3
通讯作者：
Edwards, R. Lawrence
中科院分区：
文献类型：
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作者：
Apaestegui, James;Cruz, Francisco William;Edwards, R. Lawrence
在这里，我们提出了高分辨率三角洲O-18记录从玻利维亚东部安第斯山脉的洞穴积土收集。稳定同位素记录与区域大规模的大气环流在南美洲，并允许解释在三角洲O-18在过去的1400年的变化，在南部热带安第斯山脉的降水制度的变化的函数。两个不同的阶段，更负的三角洲O-18值，解释为增加对流活动的时期在东部安第斯山脉在玻利维亚的观察伴随着全球气候异常的时期，如中世纪气候异常（MCA）和小冰期（LIA）分别。在玻利维亚三角洲O-18记录的变化在LIA显然是有关的热带辐合带（ITCZ），作为一个主要的水分驱动器，加强对流在热带大陆的向南位移。然而，在MCA期间，玻利维亚记录中观察到的对流活动增加可能是不同机制的结果，这意味着主要来自热带大西洋南部的水分。这一解释是一致的古气候记录进一步向北在热带安第斯山脉，显示在这段时间内逐渐干燥的条件下，表明更北的ITCZ的位置。MCA和LIA之间的过渡期显示出轻微的趋势，增加δ O-18值，表明对流活动减弱。我们的研究结果还揭示了一个非平稳的反相位行为之间的三角洲O-18重建从玻利维亚和巴西东北部，证实了大陆规模的东西遥相关南美洲在LIA。(C)2018 Elsevier B. V.版权所有。
Here we present high-resolution delta O-18 records obtained from speleothems collected in the eastern Bolivian Andes. The stable isotope records are related to the regional- to large-scale atmospheric circulation over South America and allow interpreting changes in delta O-18 during the last 1400 yr as a function of changes in precipitation regimes over the southern tropical Andes. Two distinct phases with more negative delta O-18 values, interpreted as periods of increased convective activity over the eastern Andean Cordillera in Bolivia are observed concomitantly with periods of global climate anomalies during the last millennium, such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) respectively. Changes in the Bolivian delta O-18 record during the LIA are apparently related to a southward displacement of the Intertropical Convergence Zone (ITCZ), which acts as a main moisture driver to intensify convection over the tropical continent. During the MCA, however, the increased convective activity observed in the Bolivian record is likely the result of a different mechanism, which implies moisture sourced mainly from the southern tropical Atlantic. This interpretation is consistent with paleoclimate records further to the north in the tropical Andes that show progressively drier conditions during this time period, indicating a more northerly position of the ITCZ. The transition period between the MCA and the LIA shows a slight tendency toward increased delta O-18 values, indicating weakened convective activity. Our results also reveal a non-stationary anti-phased behavior between the delta O-18 reconstructions from Bolivia and northeastern Brazil that confirms a continental-scale east-west teleconnection across South America during the LIA. (C) 2018 Elsevier B.V. All rights reserved.