Competing Temperature and Atmospheric Circulation Effects on Southwest Madagascan Rainfall During the Last Deglaciation
Competing Temperature and Atmospheric Circulation Effects on Southwest Madagascan Rainfall During the Last Deglaciation
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DOI：
10.1029/2018pa003466
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发表时间：
2019-02
影响因子：
3.5
通讯作者：
N. Scroxton;S. Burns;D. McGee;B. Hardt;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina
中科院分区：
文献类型：
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作者：
N. Scroxton;S. Burns;D. McGee;B. Hardt;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina
全球古季风概念预测，在存在不对称太阳强迫和/或不对称半球温度变化的时间尺度上，北半球和南半球季风降雨的反相位响应。然而，由于不同的季风系统对局地、区域和全球强迫的敏感性不同，降雨响应可能因区域而异，特别是在大的全球气候变化期间，例如在两个半球都发生变暖的最后一次消冰期。尽管夏季风在南半球扮演着与阿拉伯和印度夏季风相对应的重要角色，但在最后一次消冰期间，印度洋南半球夏季风的行为是未知的。因此，我们在马达加斯加西南部的Tsimanampesotse国家公园提出了一个新的高分辨率，精确年代和复制的洞穴稳定同位素记录，涵盖了最后一次冰川消退。研究表明，洞穴洞生长阶段主要响应南半球夏季哈德利环流（热带雨带夏季范围/平均热带辐合带位置）的运动，并在关键时期（如Bølling‐allerld）受到海面温度变化的影响。相比之下，speleothem δ18Ο主要响应海表温度，特别是深大气对流等温线的位置，而夏季哈德利环流变化起次要作用。分离温度和大气环流对控制马达加斯加西南部降雨的不同影响对于理解过去和未来的降雨变化至关重要。
The global paleomonsoon concept predicts an antiphase response of monsoon rainfall in the Northern and Southern Hemispheres at timescales where there is asymmetric solar forcing and/or asymmetric hemispheric temperature changes. However, as different monsoon systems have different sensitivities to local, regional, and global forcing, rainfall response may vary regionally, particularly during large global climatic changes such as the last deglaciation where warming occurred in both hemispheres. Despite its role as a key Southern Hemisphere counterpart to the Arabian and Indian summer monsoons, the behavior of the summer monsoon in the Southern Hemisphere of the Indian Ocean during the last deglaciation is unknown. Therefore, we present a new high‐resolution, precisely dated, and replicated speleothem stable isotope record from Tsimanampesotse National Park in southwest Madagascar that covers the last deglaciation. We show that speleothem growth phases respond largely to movements of the Southern Hemisphere summer Hadley circulation (summer extent of the tropical rainbelt/mean Intertropical Convergence Zone location), with some contribution from sea surface temperature changes at key times, such as during the Bølling‐Allerød. In contrast, speleothem δ18Ο responds primarily to sea surface temperature, in particular the location of the deep atmospheric convection isotherm, while summer Hadley circulation changes take a secondary role. Separating the varying influences of temperature and atmospheric circulation in controlling southwest Madagascan rainfall is critical to understanding rainfall variability in both the past and the future.