Collaborative Research (GRGC) Holocene Lacustrine Records of Decade-to-Century-Scale Variations in Monsoon Precipitation, Northwestern India

该项目的主要目标是利用印度西北部三个湖泊的详细沉积记录，记录和了解印度西北部季风区十年至百年尺度的古气候变化。这些湖泊中的细层状沉积物保存了过去1万至1.3万年的高分辨率湖泊水位变化的特殊记录，可能是印度季风区中最完整和详细的全新世古气候记录。这些湖泊位于干旱/半干旱的塔尔沙漠，处于夏季季风降雨主导地区的边界（Singh et al., 1990），因此对季风强度的波动特别敏感。对这些湖泊记录的分析将解决季风的年代际变化如何响应季风古气候的长期变化，提供覆盖足够长时间尺度的高分辨率记录，以充分捕捉季风系统的自然变化范围，这些信息对于了解季风区近期未来的气候变化至关重要。这是中央华盛顿大学和亚利桑那大学研究人员之间的一个合作项目。该方法包括通过结合(1)细层状沉积物的详细地层学和沉积学，(2)蒸发岩和粘土矿物学，以及(3)放射性碳定年法，重建三个浅闭盆地湖泊十年至世纪尺度的湖泊水位、盐度和沉积物流入的变化。微动物、微量元素、稳定同位素和花粉对这一问题的潜在应用将被探索和测试，但不会是研究的主要重点。这些数据，连同关于降水、地下水位、蒸发和温度的现代数据，将用于构建水文湖泊收支模型，并量化产生湖泊波动所必需的水文和气候参数的变化。分析将集中在高、低和过渡湖泊水位条件下长期保存在初级地层中的高分辨率变化。我们将重点关注具体的时期，包括(a)高变率和变化条件的内部，如干湿转换；(b)全新世晚期反映过去4000年轻微气候波动和/或极端事件的短寿浅湖；(c)湖泊水位特别高（例如4000-6000 BP）或低的时期。高分辨率古水文变化的分析将为印度、亚洲和非洲季风区全新世古气候的大尺度重建提供新的视角。

Baker 9417896 The principal objective of this project is to document and understand decade- to century-scale paleoclimatic variations in the monsoon region of northwestern India, using detailed sedimentary records from three lake in northwestern India. The finely- laminated sediments in these lakes preserve an exceptional record of high-resolution lake-level variations over the last 10,000 to 13,000 years, possibly the most complete and detailed Holocene paleoclimatic record within the Indian Monsoon region. The lakes lie in the arid/semiarid Thar Desert at the boundary of the region dominated by summer monsoon rainfall (Singh et al., 1990), and are thus particularly sensitive to fluctuations in the strength of the monsoon. Analysis of these lacustrine records will address how the decadal-scale variations in the monsoon respond to longer-term shifts in the monsoon paleoclimate, providing a high-resolution record that covers a sufficiently long time scale to fully capture the natural range of variability in the monsoon system, information that is essential for understanding near-term future climatic variations in the monsoon region. This is a collaborative project between researchers at Central Washington University and the of University of Arizona (see accompanying proposal). The methodology involves reconstructing decade- to century-scale changes in lake levels, salinity, and sediment influx in three shallow, closed-basin lakes through a combination of (1) detailed stratigraphy and sedimentology of finely laminated sediments, (2) evaporite and clay mineralogy, and (3) radiocarbon dating. Potential application of microfauna, trace elements, stable isotopes and pollen toward this problem will be explored and tested, but will not be a main focus of the study. These data, along with modern data on precipitation, water-table elevations , evaporation, and temperature, will be used to construct hydrological lake-budget models and quantify th e changes in hydrologic and climatic parameters necessary to produce the lake fluctuations. The analyses will concentrate on the high-resolution variations preserved in the primary stratigraphy during extended periods of high, low , and transitional lake-level conditions. We will emphasize specific periods of interest, including (a) internals of high variability and changing conditions, such as wet-dry transitions, (b) short-lived, shallow lakes in the late Holocene that reflect minor climatic fluctuations and/or extreme events in the last 4000 years and (c) periods of particularly high (e.g. 4000-6000 BP) or low lake levels. Analysis of the high- resolution paleohydrological variations will add a new dimension to broader-scale reconstructions of Holocene paleoclimates in monsoonal regions of India, Asia and Africa.