Spatiotemporal variability of modern precipitation δ18O in the central Andes and implications for paleoclimate and paleoaltimetry estimates
Spatiotemporal variability of modern precipitation δ18O in the central Andes and implications for paleoclimate and paleoaltimetry estimates
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DOI：
10.1002/2014jd022893
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发表时间：
2015-05-27
影响因子：
4.4
通讯作者：
Ehlers, Todd A.
中科院分区：
文献类型：
--
作者：
Fiorella, Richard P.;Poulsen, Christopher J.;Ehlers, Todd A.
了解安第斯山脉中部降雨同位素组成的模式受到稀疏观测的阻碍。尽管有限的观测数据，稳定同位素示踪剂已被普遍用于约束现代到古代安第斯山脉的大气过程，以及重建古气候和古测高历史。在这里，我们目前的同位素组成的降水（O-18（p）和D-p）从11个微气象站位于整个玻利维亚高原和沿着其东侧在类似的21.5度S。我们收集并同位素分析了293个月的散装降水样品（2008年8月至2013年4月）。O-18（p）值范围为-28.0至9.6，所有站点都表现出明显的季节性周期。我们观察到O-18（p）和海拔高度之间有很强的关系，尽管它在时间和空间上变化很大。从大气后向轨迹计算估计的空气来源的限制表明，大陆尺度的气候动力学控制的年际变化O-18（p），逆风降水异常具有最大的影响。降水异常的影响，在遥远的空气源区域的中部安第斯山脉反过来调制玻利维亚高。玻利维亚高压的重要性在玻利维亚高原南部最为明显。然而，每月的变化之间的高原站可以超过10在O-18（p）在高原上，不能解释海拔或源的变化，表明一个不平凡的作用，当地的尺度效应在短时间尺度上。大气环流对安第斯山脉中部O-18（p）的强烈影响要求古气候和古测高研究考虑南美大气古环流在解释稳定同位素值时的作用。
Understanding the patterns of rainfall isotopic composition in the central Andes is hindered by sparse observations. Despite limited observational data, stable isotope tracers have been commonly used to constrain modern-to-ancient Andean atmospheric processes, as well as to reconstruct paleoclimate and paleoaltimetry histories. Here, we present isotopic compositions of precipitation (O-18(p) and D-p) from 11 micrometeorological stations located throughout the Bolivian Altiplano and along its eastern flank at similar to 21.5 degrees S. We collected and isotopically analyzed 293 monthly bulk precipitation samples (August 2008 to April 2013). O-18(p) values ranged from -28.0 to 9.6, with prominent seasonal cycles expressed at all stations. We observed a strong relationship between the O-18(p) and elevation, though it varies widely in time and space. Constraints on air sourcing estimated from atmospheric back trajectory calculations indicate that continental-scale climate dynamics control the interannual variability in O-18(p), with upwind precipitation anomalies having the largest effect. The impact of precipitation anomalies in distant air source regions to the central Andes is in turn modulated by the Bolivian High. The importance of the Bolivian High is most clearly observed on the southern Bolivian Altiplano. However, monthly variability among Altiplano stations can exceed 10 in O-18(p) on the plateau and cannot be explained by elevation or source variability, indicating a nontrivial role for local scale effects on short timescales. The strong influence of atmospheric circulation on central Andean O-18(p) requires that paleoclimate and paleoaltimetry studies consider the role of South American atmospheric paleocirculation in their interpretation of stable isotopic values as proxies.