Hydroclimatic variability in Southeast Asia over the past two millennia
Hydroclimatic variability in Southeast Asia over the past two millennia
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DOI：
10.1016/j.epsl.2019.115737
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发表时间：
2019-11
影响因子：
5.3
通讯作者：
Jessica K. Wang;K. Johnson;A. Borsato;D. Amaya;M. Griffiths;G. Henderson;S. Frisia;A. Mason
中科院分区：
文献类型：
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作者：
Jessica K. Wang;K. Johnson;A. Borsato;D. Amaya;M. Griffiths;G. Henderson;S. Frisia;A. Mason
过去两千年来亚洲季风的时空变异性被归因于外部太阳和火山强迫和(或)内部大气-海洋耦合动力的共同作用，但这些机制的相对重要性仍未确定。目前对东南亚大陆上几十年到百年尺度的AM变率的了解并不是很受限制，尽管根据树木年轮记录在理解季节到十年的变率方面取得了实质性进展。在这里，我们提出了第一个高分辨率稳定同位素(δ13C和δ18O)洞穴记录，来自老挝北部跨越公元前50年至1880年(∼公元前)。δ13C记录揭示了主要由当地水平衡驱动的百年尺度的巨大波动。值得注意的是，我们遗址最干旱的时期发生在公元1280年至公元1430年的吴哥干旱时期，这支持了之前的发现，即这场大干旱可能影响了东南亚大陆的大部分地区。相反，石笋δ18O的变化反映了我们研究地点上游降雨的变化。有趣的是，δ18O记录与持续到1200CE之后的太阳活动呈正相关，这与以前的研究结果相反。太阳强迫气候模式模拟表明，这些δ18O变化可能是由热带印度洋上游降水的太阳强迫变化所驱动的，这些变化改变了输送到我们研究地点的水汽的δ18O，而不一定影响当地的降雨量。我们的结论是，东南亚大陆未来的降水变化可能叠加在背景气候的几十年至百年尺度的变化上，这主要是由内部气候变化驱动的，而太阳强迫可能会影响印度洋上游的降水。
The spatiotemporal variability of the Asian Monsoon (AM) over the last two millennia has been attributed to a combination of external solar and volcanic forcing and/or internal coupled atmosphere-ocean dynamics, but the relative importance of these mechanisms remains unresolved. The present knowledge of multidecadal to centennial-scale AM variability over Mainland Southeast Asia is not well-constrained, despite substantial progress in understanding seasonal to decadal variability from tree ring records. Here we present the first high-resolution stable isotope (δ 13 C and δ 18 O) speleothem record from northern Laos spanning the Common Era (∼ 50 BCE to 1880 CE). The δ 13 C record reveals substantial centennial-scale fluctuations primarily driven by local water balance. Notably, the driest period at our site occurred from∼ 1280 to 1430 CE, during the time of the Angkor droughts, supporting previous findings that this megadrought likely impacted much of Mainland Southeast Asia. In contrast, variations in stalagmite δ 18 O reflect changes in rainfall upstream from our study site. Interestingly, the δ 18 O record exhibits a positive correlation with solar activity that persists after 1200 CE, contrary to the findings in previous studies. Solar-forced climate model simulations reveal that these δ 18 O variations may be driven by solar-forced changes in upstream rainout over the tropical Indian Ocean, which modify the δ 18 O of moisture transported to our study site without necessarily affecting local rainfall amount. We conclude that future rainfall changes in Mainland Southeast Asia are likely to be superimposed on multidecadal to centennial-scale variations in background climate driven primarily by internal climate variability, whereas solar forcing may impact upstream rainout over the Indian Ocean.