Hemispherically in-phase precipitation variability over the last 1700 years in a Madagascar speleothem record
Hemispherically in-phase precipitation variability over the last 1700 years in a Madagascar speleothem record
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DOI：
10.1016/j.quascirev.2017.03.017
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发表时间：
2017-05
影响因子：
4
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
对热带降雨的古气候研究已经认识到，在轨道和千年时间尺度上，北方和南半球之间存在着一种主要的反相行为模式。不太确定的是，在全新世晚期，在边界条件和时间尺度上，区域热带降雨模式是如何变化的，这与热带地区对全球变暖的反应最相关。几个高分辨率的南半球降雨记录与平均热带辐合带位置的纬向运动不一致，这是全新世热带降雨变化的主要驱动力，区域降水模式类似于现代厄尔尼诺南方涛动的末端成员。为了验证近千年热带降水变化的新观点，需要南半球的更多记录，我们提供了一个新的洞穴沉积物δ 18O记录，它来自马达加斯加西北部的Anjohibe洞穴，提供了近1700年来季风强度和降水量的准年记录。记录中的大多数δ 18 O变化都是在十年尺度上，与主要气候指数或周期性气候驱动因素几乎没有相关性。在较低的频率，平均洞穴沉积物δ 18 O的变化表现出良好的相关性与其他区域的降水记录，北和南赤道。整个西印度洋热带降水的区域一致性类似于热带雨带的扩张和收缩以及不同时间尺度上的正印度洋偶极子状条件。这种一致性的原因可能与大陆感热的对称变化或低频海表温度气候模式有关。
Paleoclimate studies of tropical rainfall have led to a recognition of a predominant pattern of anti-phase behavior between the Northern and Southern hemispheres at both orbital and millennial timescales. Less certain is how regional tropical rainfall patterns have changed in the late Holocene, under boundary conditions and on timescales which are most relevant to the tropics' response to a warming world. Several high-resolution southern hemisphere rainfall records are at odds with meridional movement of the mean Inter-Tropical Convergence Zone location as the major driver of Holocene tropical rainfall variability, with regional precipitation patterns resembling modern day El-Niño Southern Oscillation end members. To test emerging ideas on sub-millennial tropical rainfall variability, additional records from the southern hemisphere are required.We present a new speleothem δ18O record from Anjohibe Cave, northwestern Madagascar, which provides a quasi-annual record of monsoonal strength and precipitation amount for the last 1700 years. The majority of δ18O variability in the record is at the decadal scale, and shows little to no correlation with major climate indices or cyclical climate drivers. At lower frequencies, changes in mean speleothem δ18O show good correlation with other regional precipitation records both north and south of the equator. The regional coherency of tropical rainfall across the west Indian Ocean resembles expansion and contraction of the tropical rain belt and positive-Indian Ocean Dipole-like conditions at different timescales. The cause of this coherency could be related to symmetrical changes in continental sensible heating, or to a low frequency sea surface temperature climate mode.