Tropical Indian Ocean basin hydroclimate at the Mid- to Late-Holocene transition and the double drying hypothesis
Tropical Indian Ocean basin hydroclimate at the Mid- to Late-Holocene transition and the double drying hypothesis
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DOI：
10.1016/j.quascirev.2022.107837
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发表时间：
2022-11
影响因子：
4
通讯作者：
N. Scroxton;S. Burns;D. McGee;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina;Benjamin H. Tiger
中科院分区：
文献类型：
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作者：
N. Scroxton;S. Burns;D. McGee;L. Godfrey;Lovasoa Ranivoharimanana;P. Faina;Benjamin H. Tiger
全新世气候异常的空间格局对于确定变化机制、区分非强迫和强迫气候变率以及了解对过去和未来人类社会的潜在影响至关重要。4.2 ka事件通常被认为是全新世最大和最好的记录的气候突变之一。然而，在数据丰富的北方半球中纬度地区之外，气候异常的全球模式是不确定的。在这项研究中，我们调查的空间和时间变化的热带印度洋水文气候在中晚全新世过渡。我们进行了蒙特-卡罗主成分分析，考虑全年龄的不确定性，在10个高分辨率，精确定年的古水文气候记录从热带印度洋盆地，所有连续增长或几乎连续之间5和3 kyr BP。结果表明，该地区变化的主要模式是在3.97 kyr BP（±0.08 kyr标准误差）和3.76 kyr BP（±0.07 kyr标准误差）之间的干燥，在一些记录中，干燥条件持续了300年，而在其他记录中则是永久性的变化。这种干燥的PC1，我们解释为夏季季风变化的代理，适合与以前公认的热带水文气候变化约4.0 kyr BP。在个别记录中，局部观察到了4.2至3.9 kyr BP的突发事件，但缺乏区域一致性。热带印度洋水文气候中缺乏明显的4.2 ka事件对印度河流域的气候变异性和哈拉帕文明产生了影响。通过对印度次大陆现有古气候记录、印度夏季风和冬季西风扰动源区上游气候变率以及现代气候学的比较，提出了“双重干燥假说”。4.2和3.9 kyr BP之间的冬季降雨干燥，其次是3.97 kyr BP和至少3.4 kyr BP之间的夏季降雨干燥。双重干燥假说为哈拉帕文明提供了更详细的气候背景，解决了作物悖论，并符合城市废弃的时空模式。探讨了新的中晚全新世全球边界层型剖面和梅加拉亚石笋点的结果。
The spatial pattern of Holocene climate anomalies is crucial to determining the mechanisms of change, distinguishing between unforced and forced climate variability, and understanding potential impacts on past and future human societies. The 4.2 ka event is often regarded as one of the largest and best documented abrupt climate disturbances of the Holocene. Yet outside the data-rich Northern Hemisphere mid-latitudes, the global pattern of climate anomalies is uncertain. In this study we investigate the spatial and temporal variability of the tropical Indian Ocean hydroclimate at the Mid- to Late-Holocene transition. We conducted Monte-Carlo principal component analysis, considering full age uncertainty, on ten high-resolution, precisely dated paleohydroclimate records from around the tropical Indian Ocean basin, all growing continuously or almost continuously between 5 and 3 kyr BP. The results indicate the dominant mode of variability in the region was a drying between 3.97 kyr BP (±0.08 kyr standard error) and 3.76 kyr BP (±0.07 kyr standard error) with dry conditions lasting for an additional 300 years in some records, and a permanent change in others. This drying in PC1, which we interpret as a proxy of summer monsoon variability, fits with a previously recognised tropic wide change in hydroclimate around 4.0 kyr BP. An abrupt event from 4.2 to 3.9 kyr BP is seen locally in individual records but lacks regional coherence.A lack of apparent 4.2 ka event in tropical Indian Ocean hydroclimate has ramifications for climate variability in the Indus valley, and for the Harappan civilization. Through a comparison of existing Indian subcontinent paleoclimate records, upstream climatic variability in the Indian Summer Monsoon and winter Westerly Disturbances source regions, and modern climatology, we present the “Double Drying hypothesis”. A winter rainfall drying between 4.2 and 3.9 kyr BP was followed by a summer rainfall drying between 3.97 kyr BP and at least 3.4 kyr BP. The Double Drying hypothesis provides more detailed climatic context for the Harappan civilization, resolves the cropping paradox, and fits the spatial-temporal pattern of urban abandonment. The consequences for the new Mid- to Late-Holocene Global Boundary Stratotype Section and Point in a stalagmite from Meghalaya are explored.