Zhe Sun, Zirui Huang, Kejia Ji, Mingda Wang, Juzhi Hou
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The core was dated using AMS <sup>14</sup>C and Pb/Cs methods, and we used measurements of element contents (determined by high-resolution XRF scanning), grain size, IC/TOC, and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since ∼4000 yr ago. Combined with a modern meteorological data set, we found that PC1 of the XRF data, the Ca/(Fe + Ti) ratio, and EM1 of the grain size data were indicative of changes in humidity. Our records demonstrate a wet interval during ∼4−1.7 ka BP (ka = 1000 yr, BP represents years before 1950 AD), followed by a dry period during since ∼1 ka BP. Comparison with independent regional paleoclimatic records revealed shifts in the dominant factors controlling humidity. The wet interval during ∼4−1.7 ka BP was coeval with a strengthened Westerlies, implying a dominant moisture supply from northern high latitudes. However, the extremely low values of Ca/(Fe + Ti) ratio during ∼4−2.5 ka BP indicate potential glacial freshwater source, which is corroborated by the concurrent high magnetic susceptibility values and increased grain size. The rapid drying trend during ∼1.7−1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon (ISM). We attribute the drought conditions after ∼1 ka BP to a weakened ISM, although a Westerlies influence and the potential effect of high temperatures on evaporation cannot be excluded. We suggest that future hydroclimatic research in this region should attempt to distinguish the individual moisture contributions of the ISM and the Westerlies during the last millennium.</p>","PeriodicalId":48927,"journal":{"name":"Frontiers of Earth Science","volume":null,"pages":null},"PeriodicalIF":1.8000,"publicationDate":"2023-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Alternating influences of the Westerlies and Indian Summer Monsoon on the hydroclimate of the source region of the Yarlung Tsangpo over past 4000 yr\",\"authors\":\"Zhe Sun, Zirui Huang, Kejia Ji, Mingda Wang, Juzhi Hou\",\"doi\":\"10.1007/s11707-022-1055-5\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<p>The Yarlung Tsangpo, the longest river in the southern Tibetan Plateau (TP), has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate change. 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引用次数: 0
摘要
雅鲁藏布江是青藏高原南部(TP)最长的河流,其现代水文和未来可能的排水量的控制因素在当前气候变化的背景下吸引了大量研究人员的关注。然而,部分由于复杂的区域气候背景,尚未得出一致的结论,尤其是对其上游而言。对雅鲁藏布江源头地区进行古水文重建,有可能加深我们对湿度历史及其对气候变异反应的理解。在本研究中,我们使用了来自公珠公司的 97 厘米重力岩芯来重建全新世晚期的水文变化。利用 AMS 14C 和 Pb/Cs 方法对岩心进行了年代测定,并通过测量元素含量(通过高分辨率 XRF 扫描确定)、粒度、IC/TOC 和磁感应强度,重建了雅鲁藏布江流域源头自 4000 年前以来的水文气候变迁。结合现代气象数据集,我们发现 XRF 数据的 PC1、Ca/(Fe + Ti)比值和粒度数据的 EM1 都表明了湿度的变化。我们的记录表明,在公元前 4-1.7 ka(ka = 1000 年,BP 代表公元 1950 年之前的年份)期间是一个湿润时期,而自公元前 1 ka 起则是一个干燥时期。通过与独立的区域古气候记录进行比较,发现控制湿度的主要因素发生了变化。公元前 4-1.7 ka年间的湿润期与西风增强同时出现,这意味着湿气主要来自北部高纬度地区。然而,公元前 4-2.5 ka年间的钙/(铁+钛)比值极低,表明可能有冰川淡水来源,同时出现的高磁感值和粒径增大也证实了这一点。1.7-1 ka BP期间的快速干燥趋势表明,水汽供应已从西风转向印度夏季季风(ISM)。我们将公元前 1 ka 年之后的干旱状况归因于 ISM 的减弱,尽管不能排除西风的影响以及高温对蒸发的潜在影响。我们建议,该地区未来的水文气候研究应尝试区分 ISM 和西风在上一个千年期间对水汽的贡献。
Alternating influences of the Westerlies and Indian Summer Monsoon on the hydroclimate of the source region of the Yarlung Tsangpo over past 4000 yr
The Yarlung Tsangpo, the longest river in the southern Tibetan Plateau (TP), has attracted much research attention aimed at understanding the factors controlling its modern hydrology and possible future discharge in the context of ongoing climate change. However, partly due to the complex regional climatic background, no consistent conclusions have been reached, especially for its upper reaches. Paleohydrological reconstructions of the source region of the Yarlung Tsangpo can potentially improve our understanding of the history of humidity and its response to climatic variability. In this study, we used a 97 cm gravity core from Gongzhu Co to reconstruct the hydrology change during the late Holocene. The core was dated using AMS 14C and Pb/Cs methods, and we used measurements of element contents (determined by high-resolution XRF scanning), grain size, IC/TOC, and magnetic susceptibility to reconstruct hydroclimatic changes in the source of the Yarlung Tsangpo watershed since ∼4000 yr ago. Combined with a modern meteorological data set, we found that PC1 of the XRF data, the Ca/(Fe + Ti) ratio, and EM1 of the grain size data were indicative of changes in humidity. Our records demonstrate a wet interval during ∼4−1.7 ka BP (ka = 1000 yr, BP represents years before 1950 AD), followed by a dry period during since ∼1 ka BP. Comparison with independent regional paleoclimatic records revealed shifts in the dominant factors controlling humidity. The wet interval during ∼4−1.7 ka BP was coeval with a strengthened Westerlies, implying a dominant moisture supply from northern high latitudes. However, the extremely low values of Ca/(Fe + Ti) ratio during ∼4−2.5 ka BP indicate potential glacial freshwater source, which is corroborated by the concurrent high magnetic susceptibility values and increased grain size. The rapid drying trend during ∼1.7−1 ka BP suggests a switch in moisture supply from the Westerlies to the Indian Summer Monsoon (ISM). We attribute the drought conditions after ∼1 ka BP to a weakened ISM, although a Westerlies influence and the potential effect of high temperatures on evaporation cannot be excluded. We suggest that future hydroclimatic research in this region should attempt to distinguish the individual moisture contributions of the ISM and the Westerlies during the last millennium.
期刊介绍:
Frontiers of Earth Science publishes original, peer-reviewed, theoretical and experimental frontier research papers as well as significant review articles of more general interest to earth scientists. The journal features articles dealing with observations, patterns, processes, and modeling of both innerspheres (including deep crust, mantle, and core) and outerspheres (including atmosphere, hydrosphere, and biosphere) of the earth. Its aim is to promote communication and share knowledge among the international earth science communities