Branched glycerol dialkyl glycerol tetraethers (brGDGTs) in lake sediments are increasingly being used to reconstruct past temperatures. However, recent studies suggest that brGDGT distributions and concentrations vary with lake size and environmental conditions, such as seasonality and its effects on water column temperature and chemistry. To test their use as a paleothermometer in high-altitude environments of mid-latitude North America, we analyzed brGDGT distributions in lake surface sediments across a range of lake depths and elevations in the Rocky Mountains of Wyoming and Colorado. Our results suggest that brGDGT distributions and the MBT′_5Me index correlate with water column temperatures, which are sensitive to both lake water depth and air temperatures. Based on these relationships, we developed a calibration to mean summer air temperatures using a Bayesian regression model that incorporates the MBT′_5Me index and lake water depth. We applied our calibration to lake sediments from Lower Paintrock Lake in northern Wyoming to test its use as a paleothermometer. Reconstructed temperature trends are consistent with pollen-inferred temperatures at the same site and with known regional climate history, demonstrating that our calibration can be successfully applied to infer temperatures in high-altitude environments of mid-latitude North America.

湖泊沉积物中的支链甘油二烷基甘油四醚（brGDGTs）越来越多地用于重建过去的温度。但是，最近的研究表明，brGDGT的分布和浓度随湖泊大小和环境条件（例如季节及其对水柱温度和化学的影响）而变化。为了测试它们在北美洲中纬度高海拔环境中作为古温度计的用途，我们分析了怀俄明州和科罗拉多州落基山脉一系列湖泊深度和海拔范围内，brGDGT在湖泊表面沉积物中的分布。我们的结果表明brGDGT分布和_MBT'5Me指数与水柱温度相关，而水柱温度对湖泊水深和气温都敏感。基于这些关系，我们使用结合了_MBT'5Me指数和湖泊水深的贝叶斯回归模型开发了一个夏季平均气温的标定。我们将校准技术应用于怀俄明州北部Lower Paintrock湖的湖泊沉积物，以测试其用作古温度计的用途。重构后的温度趋势与同一地点的花粉推断温度以及已知的区域气候历史相吻合，这表明我们的校准可以成功地应用于推断北美中纬度高海拔环境中的温度。