Monsoon source shifts during the drying mid-Holocene: Biomarker isotope based evidence from the core ‘monsoon zone’ (CMZ) of India
Monsoon source shifts during the drying mid-Holocene: Biomarker isotope based evidence from the core ‘monsoon zone’ (CMZ) of India
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全新世中期干燥期间季风源发生变化：来自印度核心“季风区”（CMZ）的基于生物标记同位素的证据
DOI：
10.1016/j.quascirev.2015.06.020
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发表时间：
2015
影响因子：
4
通讯作者：
Sachse
中科院分区：
文献类型：
--
作者：
Sarkar;Prasad;Wilkes;Riedel;Stebich;Basavaiah;Sachse
更好地了解印度夏季风(ISM)的过去变化，可以更好地评估其在全球气候变化情景下的潜在影响。印度夏季风对印度仍然主要以农业为主的经济起着至关重要的作用。然而，由于缺乏高分辨率的大陆古水文记录，我们对ISM强度的时空模式的了解有限。在这里，我们重建了全新世期间与ISM强度变化相关的百年尺度水文变异性，其基础是来自位于印度中部核心季风带的盐碱洛纳尔湖的一个10米长沉积物岩芯的脂类生物标志物丰度和化合物特有的稳定同位素组成的记录。我们确定了印度中部全新世三个不同的水文时期。10.1至6大卡BP之间的时期可能是全新世最潮湿的。叶WAXN-烷烃的平均链长指数较低(29.4-28.6)和负δ13Cwax值(−34.8‰至−27.8‰)表明流域内木本C3植被占优势，负δDwax值(浓度加权平均)(−171‰至−147‰)表明季风增强导致的湿润期。在6千卡BP后，逐渐转向较不负的δ13Cwax值(特别是草类衍生的n-C31)和三萜类脂四氢甘露醇的出现，通常被认为是盐度和水柱分层的标志，标志着更干燥条件的开始。在5.1千卡BP，叶WAXN-烷烃通量的增加以及四氢甘露醇通量的最大值表明湖泊水位的大幅下降。在4.8至4千卡BP之间，我们发现了向干旱条件过渡的证据，这表明四氢甘露醇通量高且变化强烈。此外，在此期间，δ13Cwax值明显转向较低的负值，特别是FORN-C31(−25.2‰到−22.8‰)，这表明优势植被向C4草类转变。与其他替代数据一致，例如蒸发岩矿物的沉积，我们将这一时期解释为反映了该地区在过去10.1百万年期间最干燥的条件。这一过渡导致了4 Ka后持续的晚全新世干旱条件，存在永久盐湖，并得到了四氢甘露醇的持续存在和更正的平均δDwax值(−122‰至−141‰)的支持。在全新世晚期，蓝藻生物标志物输入的峰值为1.3千卡BP，这可能代表了湖泊富营养化事件，可能是由于人类的影响和集水区牛畜养殖的开始。我们记录的一个独特特征是在4.8千卡BP和4千卡BP之间存在一个明显的过渡期，其特征是在全新世(最高为1.3千卡BP)，一些最负的δDwax值，而所有其他替代数据表明全新世期间最干燥的条件。这些负的δDwax值可以最合理地解释为在这一过渡期内水汽来源区域和/或路径或降雨季节性的变化。我们假设，轨道引起的夏季太阳辐射的减弱和与之相关的大气环流的重组，作为热带雨带的可能南移，导致了印度中部4.8至4 Kb之间的不稳定水文气候。我们的发现揭示了一旦超过太阳辐射驱动的阈值，季风系统平均状态变化期间的变化序列，并表明太阳辐射的微小变化可以与大陆上的主要水气候变化有关，这一情景可能与未来…的变化有关
A better understanding of past variations of the Indian Summer Monsoon (ISM), that plays a vital role for the still largely agro-based economy in India, can lead to a better assessment of its potential impact under global climate change scenarios. However, our knowledge of spatiotemporal patterns of ISM strength is limited due to the lack of high-resolution, continental paleohydrological records. Here, we reconstruct centennial-scale hydrological variability during the Holocene associated to changes in the intensity of the ISM based on a record of lipid biomarker abundances and compound-specific stable isotopic composition of a 10 m long sediment core from saline–alkaline Lonar Lake, situated in the core ‘monsoon zone’ of central India.We identified three main periods of distinct hydrology during the Holocene in central India. The period between 10.1 and 6 cal ka BP was likely the wettest during the Holocene. Lower average chain length (ACL) index values (29.4–28.6) and negative δ13Cwaxvalues (−34.8‰ to −27.8‰) of leaf waxn-alkanes indicate the dominance of woody C3vegetation in the catchment, and negative δDwaxvalues (concentration weighted average) (−171‰ to −147‰) suggest a wet period due to an intensified monsoon. After 6 cal ka BP, a gradual shift to less negative δ13Cwaxvalues (particularly for the grass derivedn-C31) and appearance of the triterpene lipid tetrahymanol, generally considered as a marker for salinity and water column stratification, mark the onset of drier conditions. At 5.1 cal ka BP an increasing flux of leaf waxn-alkanes along with the highest flux of tetrahymanol indicate a major lowering of the lake level. Between 4.8 and 4 cal ka BP, we find evidence for a transition to arid conditions, indicated by high and strongly variable tetrahymanol flux. In addition, a pronounced shift to less negative δ13Cwaxvalues, in particular forn-C31(−25.2‰ to −22.8‰), during this period indicates a change of dominant vegetation to C4grasses. In agreement with other proxy data, such as deposition of evaporite minerals, we interpret this period to reflect the driest conditions in the region during the last 10.1 ka. This transition led to protracted late Holocene arid conditions after 4 ka with the presence of a permanent saline lake, supported by the sustained presence of tetrahymanol and more positive average δDwaxvalues (−122‰ to −141‰). A late Holocene peak of cyanobacterial biomarker input at 1.3 cal ka BP might represent an event of lake eutrophication, possibly due to human impact and the onset of cattle/livestock farming in the catchment.A unique feature of our record is the presence of a distinct transitional period between 4.8 and 4 cal ka BP, which was characterized by some of the most negative δDwaxvalues during the Holocene (up to −180‰), when all other proxy data indicate the driest conditions during the Holocene. These negative δDwaxvalues can as such most reasonably be explained by a shift in moisture source area and/or pathways or rainfall seasonality during this transitional period. We hypothesize that orbital induced weakening of the summer solar insolation and associated reorganization of the general atmospheric circulation, as a possible southward displacement of the tropical rainbelt, led to an unstable hydroclimate in central India between 4.8 and 4 ka.Our findings shed light onto the sequence of changes during mean state changes of the monsoonal system, once an insolation driven threshold has been passed, and show that small changes in solar insolation can be associated with major hydroclimate changes on the continents, a scenario that may be relevant with respect to future changes in the …
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影响因子：
2.3
作者：
Anoop, A.;Prasad, S.;Brauer, A.
通讯作者：
Brauer, A.
影响因子：
4
作者：
Fleitmann, Dominik;Burns, Stephen J.;Matter, Albert
通讯作者：
Matter, Albert
影响因子：
5.3
作者：
Prasad, Sushma;Anoop, A.;Stebich, M.
通讯作者：
Stebich, M.
湖泊有机质氢同位素比记录的美国中西部晚冰期气候
影响因子：
56.9
作者：
R. Krishnamurthy;K. Syrup;M. Baskaran;A. Long
通讯作者：
A. Long
影响因子：
2.2
作者：
Nils Riedel;M. Stebich;A. Anoop;N. Basavaiah;P. Menzel;Sushma Prasad;D. Sachse;S. Sarkar;M. Wiesner
通讯作者：
Nils Riedel;M. Stebich;A. Anoop;N. Basavaiah;P. Menzel;Sushma Prasad;D. Sachse;S. Sarkar;M. Wiesner