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

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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.