Northern circumpolar permafrost thaw affects global carbon cycling, as large amounts of stored soil carbon becomes accessible to microbial breakdown under a warming climate. The magnitude of carbon release is linked to the extent of permafrost thaw, which is locally variable and controlled by soil thermodynamics. Soil thermodynamic properties, such as thermal diffusivity, govern the reactivity of the soil-atmosphere thermal gradient, and are controlled by soil composition and drainage. In order to project permafrost thaw for an Alaskan tundra experimental site, we used seven years of site data to calibrate a soil thermodynamic model using a data assimilation technique. The model reproduced seasonal and interannual temperature dynamics for shallow (5–40 cm) and deep soil layers (2–4 m), and simulations of seasonal thaw depth closely matched observed data. The model was then used to project permafrost thaw at the site to the year 2100 using climate forcing data for three future climate scenarios (RCP 4.5, 6.0, and 8.5). Minimal permafrost thawing occurred until mean annual air temperatures rose above the freezing point, after which we measured over a 1 m increase in thaw depth for every 1 °C rise in mean annual air temperature. Under no projected warming scenario was permafrost remaining in the upper 3 m of soil by 2100. We demonstrated an effective data assimilation method that optimizes parameterization of a soil thermodynamic model. The sensitivity of local permafrost to climate warming illustrates the vulnerability of sub-Arctic tundra ecosystems to significant and rapid soil thawing.

中文翻译：

---

使用经过现场测量校准的热力学模型预测亚北极苔原的永久冻土融化

北极圈极地永久冻土融化影响全球碳循环，因为在气候变暖下，大量储存的土壤碳变得容易被微生物分解。碳释放的幅度与永久冻土融化的程度有关，后者是局部可变的，并受土壤热力学控制。土壤热力学特性，例如热扩散率，控制着土壤-大气热梯度的反应性，并受土壤成分和排水系统的控制。为了预测阿拉斯加苔原实验场地的永久冻土融化，我们使用了七年的场地数据，通过数据同化技术校准了土壤热力学模型。该模型再现了浅层（5-40 cm）和深层（2-4 m）的季节性和年际温度动态，季节性解冻深度的模拟与观测数据密切匹配。然后，该模型用于使用三种未来气候情景（RCP 4.5、6.0 和 8.5）的气候强迫数据，将该地点的永久冻土融化预测到 2100 年。最小的永久冻土融化发生到年平均气温升至冰点以上，之后我们测量到每 1 年融化深度增加超过 1 m ° C 年平均气温上升。在没有预测的变暖情景下，到 2100 年，土壤上部 3 m 中仍存在永久冻土。我们展示了一种有效的数据同化方法，可以优化土壤热力学模型的参数化。当地永久冻土对气候变暖的敏感性说明了亚北极苔原生态系统对显着和快速土壤解冻的脆弱性。