Soil and Air Temperature Calibrations Using Branched GDGTs for the Tropical Andes of Colombia: Toward a Pan‐Tropical Calibration
Soil and Air Temperature Calibrations Using Branched GDGTs for the Tropical Andes of Colombia: Toward a Pan‐Tropical Calibration
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DOI：
10.1029/2020gc008941
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发表时间：
2020-07
期刊：
影响因子：
3.7
通讯作者：
L. Pérez‐Angel;J. Sepúlveda;P. Molnar;C. Montes;B. Rajagopalan;K. Snell;C. González‐Arango;N. Dildar
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文献类型：
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作者：
L. Pérez‐Angel;J. Sepúlveda;P. Molnar;C. Montes;B. Rajagopalan;K. Snell;C. González‐Arango;N. Dildar
支链甘油二烷基甘油四醚（brGDGTs）是一种细菌细胞膜脂，当保存在沉积档案中时，可以用来推断大陆的古温度。尽管常用的全球校准捕获了brGDGTs分布与温度之间的关系，但它们低估了热带地区的温度高达~16°C。此外，一些全球校准在24-25°C左右达到饱和，而且，一般来说，它们的均方根误差（rmse≈~4°C）太大，无法解决热带地区古气候变率的小变化。我们在哥伦比亚东部科迪勒拉山脉的北部热带安第斯山脉两侧沿高度样带进行了土壤brdgts的原位区域校准，海拔约3200米，年平均土壤和空气温度分别为17°C和19°C。这些新的土壤和空气区域校准的均方根误差分别为1.5°C和1.9°C。当与来自热带其他地区的现有数据相结合时，综合数据（n = 175）不仅适合RMSE为2.7°C的线性校准，也适合RMSE为2.2°C的非线性校准。这些校准可以比全球校准更精确和可靠地重建热带地区过去的温度。
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are bacterial cell membrane lipids that, when preserved in sedimentary archives, can be used to infer continental paleotemperatures. Although commonly used global calibrations capture a relationship between the distribution of brGDGTs and temperature, they underestimate temperatures for tropical regions as much as ~16°C. Furthermore, some global calibrations reach saturation at around 24–25°C, and, in general, they have root‐mean‐squared errors (RMSEs ≈ ~4°C) that are too large for them to resolve small variations in paleoclimate variability in tropical regions. We present an in situ regional calibration of soil brGDGTs along altitudinal transects on both flanks of the Eastern Cordillera of Colombia in the northern tropical Andes that spans ~3,200 m in elevation and 17°C and 19°C in mean annual soil and air temperatures, respectively. These new soil and air regional calibrations yield RMSEs of 1.5°C and 1.9°C, respectively. When combined with existing data from elsewhere in the tropics, the integrated data (n = 175) not only fit a linear calibration with a RMSE of 2.7°C but also fit a nonlinear calibration with a RMSE of 2.2°C. These calibrations allow for a more precise and reliable reconstruction of past temperatures in the tropics than global calibrations.