Collaborative Research: Testing Potential of Paired Lakes on the NE Tibetan Plateau for Studying Interaction Between Hydrochemical Evolution and Environmental Change

湖水化学成分的演变是由入湖水和随后的蒸发浓缩以及矿物的沉淀决定的。在封闭盆地湖泊中，蒸发浓度主要由区域气候变化引起的干燥度变化决定。然而，湖水和地下水化学、湖泊沉积物地球化学和环境变化之间的相互作用在短时间或长时间尺度上都没有得到研究，也很少采用多学科的方法。这项初步研究是为了调查干旱的青藏高原东北部的成对湖泊(淡水和盐湖)。这些湖泊可能是研究水的同位素和元素演化，以及环境变化和湖泊地球化学过程相互作用的理想场所。拟议研究的首要目标是了解水化学演变及其在不同时间尺度上如何与各种环境控制相互作用。在这个靠近东亚季风北端的气候敏感地区进行这项研究的额外好处是提高了我们读取该地区湖泊沉积记录的能力，以更好地了解过去的环境变化。我们建议用多学科的方法从区域和流域尺度上研究这两个湖泊的现代过程，从矿物学和自生和生物矿物的化学和同位素组成研究溶质和水通量的历史，从孢粉、植物宏观化石和环境磁学等景观过程的记录中研究介形类动物的物种组合和气候和环境变化的历史。这一项目的结果将为理解片状溶质演化和水通量的途径和机制以及它们如何影响过去环境变化的沉积记录提供见解。这是第一个采用多学科方法来解决中亚地区湖泊-气候相互作用的研究。该项目的一个主要特点是使用成对的湖水和化学对比湖泊，以揭示湖泊水文和水化学过程与环境(和气候)变化之间的相互作用。淡水湖(科鲁克湖)与盐湖(托森湖)的现代响应研究将使古水化学的全面和广泛的重建成为可能。此外，拟议研究中使用的多种技术将提供区域气候变化、流域稳定性和植被以及湖泊化学变化的独立记录。这些记录的整合将使我们能够重点关注这些过程在不同时间尺度(从现在到冰间冰川周期)之间的复杂相互作用和反馈。我们的跨学科研究将促进对这些系统在不同气候制度下的复杂相互作用的理解。了解湖泊和分水岭对过去气候变化的反应将有助于我们预测气候(特别是季风)变化和变异性的环境后果。我们使用淡水和盐湖成对对比水化学的方法并不常用，但我们相信这是一种非常有启发性的方法，具有很大的回报。了解水文动态，将有利于中国这一偏远干旱地区的人们适应未来可能发生的气候和水文循环变化。结果将与大平原北部半干旱地区湖泊对气候和水文变化的反应进行比较，并与国家地质调查和水利委员会分享。一旦过了试点阶段，研究生和本科生将更全面地参与该项目，并将受益于与国际多学科研究团队的互动。该项目将促进合作，特别是与我们的中国同事的合作，他们在国际科技界的影响力越来越大。

The evolution of the chemical composition of lake waters is determined by the inflow waters andsubsequent evaporative concentration and the precipitation of minerals. In closed-basin lakes, evaporativeconcentration is mostly determined by changes in aridity, as a result of regional climate change. However,the interactions among lake water and groundwater chemistries, lake sediment geochemistry, andenvironmental change have not been studied over short or long time scales, and seldom usingmultidisciplinary approach.Intellectual merits. This pilot study is to investigate paired chemically-contrasting lakes (fresh andsaline) in the arid northeastern Tibetan Plateau. These lakes are likely to be ideal sites for the study ofwater isotopic and elemental evolution, and the interactions of environmental change and lacustrinegeochemical processes. The overarching objective of the proposed study is to understand hydrochemicalevolution and how it interacts with various environmental controls at different time scales. The addedbonus for undertaking such a study in this climate-sensitive region near the northern limit of the EastAsian monsoon is to improve our ability to read the lacustrine sediment record of this region to betterunderstand the past environmental changes. We propose to use a multidisciplinary approach to investigateat regional and watershed scales, the modern processes in these two lakes, history of solute and water fluxfrom mineralogy and chemical and isotopic composition of authigenic and biogenic minerals, and fromspecies assemblage of ostracodes and the history of climate and environmental change from such recordsof landscape processes as pollen, plant macrofossils, and environmental magnetism.The results from this project will provide insights into understanding the pathways and mechanisms oflake solute evolution and water flux and how they affect the sedimentary record of past environmentalchanges. This is the first study to employ a multidisciplinary approach to address the lake-climateinteractions in Central Asia. A key feature of this project is in its use of paired limnologically- andchemically-contrasting lakes in order to unravel the interactions between lacustrine hydrologic andhydrochemical processes and environmental (and climatic) changes. The study of modern responses ofthe dilute lake (Keluke Lake) with a saline Lake (Toson Lake) will enable comprehensive and robustreconstructions of paleohydrochemistry. Also, the multiple techniques used in the proposed study willprovide independent records of regional climate change, watershed stability and vegetation, as well aschanges in lake chemistry. Integration of these records will allow us to focus on the complex interactionsand feedbacks between these processes at different temporal scales (from present-day to interglacialglacialcycles).Broader impacts. Our interdisciplinary research will advance the understanding of complex interactionsin these systems under different climate regimes. Understanding the lake and watershed responses toclimate change of the past will contribute to our ability to predict the environmental consequences ofclimate (especially monsoon) variations and variability. Our approach of using contrastinghydrochemistries of paired fresh and saline lakes is not commonly employed but we believe is a veryinstructive one with a large pay-off. Understanding the hydrological dynamics will benefit the people inthis remote arid part of China in adapting to the potential future changes in climate and hydrologicalcycles. The results will be compared with the response of lakes in the semi-arid northern Great Plains toclimate and hydrololgic changes and shared with the state geological surveys and water commissions.Once past the pilot-stage, graduate and undergraduate students will be more fully involved in the projectand will benefit from interacting with an international multidisciplinary research team. The project willfacilitate collaborations, especially with our Chinese colleagues, who are having increased impacts in theinternational scene of science and technology.