Mountains are among the most sensitive ecosystems to climate change, and one of the most evident signs of climate-related effect is the continuous net loss of ice from the cryosphere. Several studies showed that meltwater from glaciated and perennially frozen areas can profoundly affect alpine aquatic ecosystems. Here, we present the impressive temporal increase in solutes in Lake Leit, a mountain lake in the Central Alps that is impacted by an active rock glacier. During the last 30 years, concentrations of sulfate and base cations increased by factors of 4 and 3, respectively. Atmospheric deposition, the only catchment external source, could be excluded as possible cause. The inlets have sulfate and base cations concentrations that were up to double the concentrations of the lake outlet confirming the presence of catchment internal sources. The highest concentrations were measured in the springs at the bottom of the rock glacier. Ground surface temperatures of the rock glacier indicated a high probability of permafrost occurrence, while the annual mean air temperature after the mid-1980s showed continuously positive deviations from the long-term average values (period 1961–1990) with increasing values after 2010. δ³⁴S of sulfate in the inlets and the outflow indicated that sulfate in Lake Leit mainly derived from dissolution of gypsum/anhydrite even if its presence is not confirmed by the Geologic Atlas of Switzerland. Because of these results, we postulate the presence of subsurface traces of sulfate-bearing evaporites, probably associated with Triassic metasediments. These deposits are very common in the closer surroundings. We further hypothesize that the thawing of permafrost affects the flow path of water enabling its contact with fresh highly weatherable minerals increasing the overall weathering rate and shifting the relative ionic composition in the discharge toward the ions that originate from the most soluble minerals. This study shows that increased permafrost thawing in the future can influence water quality in high-alpine settings.

山区是对气候变化最敏感的生态系统，而与气候有关的影响最明显的迹象之一是冰冻圈中冰的持续净损失。多项研究表明，冰川和常年冰冻地区的融水可以深刻影响高山水生生态系统。在这里，我们介绍了莱特湖溶质随时间的显着增加，莱特湖是中部阿尔卑斯山的一个高山湖泊，受到活跃的岩石冰川的影响。在过去的30年中，硫酸盐和碱性阳离子的浓度分别增加了4倍和3倍。大气沉积物是唯一的集水外部来源，可能被排除在外。进口处的硫酸盐和碱性阳离子浓度高达湖泊出口浓度的两倍，这证实了流域内部来源的存在。在岩石冰川底部的弹簧中测得的最高浓度。岩石冰川的地表温度表明存在多年冻土的可能性很高，而1980年代中期以后的年平均气温与长期平均值（1961-1990年）之间呈现出连续的正偏差，2010年以后则呈上升趋势。³⁴进水口和出水口中的硫酸盐S表明，莱特湖中的硫酸盐主要来自石膏/硬石膏的溶解，即使瑞士地质图集未确认其存在也是如此。由于这些结果，我们推测存在含硫酸盐的蒸发物的地下痕迹，这可能与三叠纪的沉积物有关。这些沉积物在较近的环境中非常普遍。我们进一步假设永久冻土的融化会影响水的流动路径，从而使其与新鲜的高度耐候矿物接触，从而提高了整体耐候率并使放电中的相对离子组成向源自最易溶矿物的离子转移。这项研究表明，未来冻土融化的增加会影响高高山地区的水质。