COLLABORATIVE RESEARCH: (GRGC) Holocene Lacustrine Records of Decade- to Century-Scale Variation in Monsoon Precipitation, Northwestern India

Ely 9418189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。这些湖泊中的细纹沉积物保存了过去10,000至13,000年来高分辨率湖泊水位变化的特殊记录，可能是印度季风区内最完整和最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，位于夏季季风降雨占主导地位的区域的边界(Singh等人，1990年)，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探讨季风的十年尺度变化如何对季风古气候的较长期变化作出反应，从而提供覆盖足够长的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的研究人员合作的项目(见随附的提案)。该方法包括通过(1)精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)放射性碳测年，重建三个封闭盆地浅水湖泊的湖平面、盐度和沉积物流入在十年到百年尺度上的变化。将探索和测试微型动物、微量元素、稳定同位素和花粉在这一问题上的潜在应用，但不会成为研究的主要重点。这些数据，以及关于降水、地下水位、蒸发和温度的现代数据，将被用来构建水文湖泊收支模型，并量化产生湖泊波动所需的水文和气候参数的变化。分析将集中在高、低和过渡湖面条件下长时间保存在原始地层中的高分辨率变化。我们将强调具体的研究时期，包括(A)高变异性和不断变化的条件的内部，例如干湿过渡，(B)全新世晚期的短暂浅湖，反映了过去4000年的轻微气候波动和/或极端事件，以及(C)特别高(例如4000-6000 BP)或低湖平面的时期。对高分辨率古水文变化的分析将为更广泛地重建印度、亚洲和非洲季风区的全新世古气候增加一个新的维度。

Ely 9418189 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 reconstructine 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 the changes in hydro logic 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.