为揭示深季节冻土区高速铁路抗冻胀基床结构的效果和稳定性，确保高速列车在冬季的安全运营，以我国深季节冻土区高速铁路典型抗冻胀基床结构为研究对象，通过现场试验和理论分析相结合的方法，研究深季节冻土区抗冻胀基床结构水热力学行为演变的内在机理，分析深季节冻土区高铁路基工程温度场非对称的一般特征，讨论影响寒区路基工程阴阳坡效应的关键因素。研究结果表明：1)季节冻融层和非冻结层的地温和横向温差随时间推移均呈现正弦规律变化。2)当基床表层和底层温度接近0℃时，对应土层内的未冻水含量迅速减小或增加。3)冻胀主要发生在冻结初期和冻融交替期。同时，融沉的结束时间滞后于冻结层的消失时间。4)不同深度处阴阳肩的温差在全年均大于0℃，影响寒区路基工程阴阳坡效应的主要因素是线路走向和主风向。综上所述，建议深季节冻土区的高速列车在冻结初期和冻融交替期减速行驶。同时，为减弱路基阴阳坡效应引起的横向非均匀变形，路基两侧应采取非对称设计的原则。

As a buffer layer for the energy and water exchange between atmosphere and permafrost, the active layer is sensitive to climate warming. Changes in the thermal state in active layer can alter soil organic carbon (SOC) dynamics. It is critical to identify the response of soil microbial communities to warming to better predict the regional carbon cycle under the background of global warming. Here, the active layer soils collected from a wetland-forest ecotone in the continuous permafrost region of Northeastern China were incubated at 5 and 15 degrees C for 45 days. High-throughput sequencing of the 16S rRNA gene was used to examine the response of bacterial community structure to experimental warming. A total of 4148 OTUs were identified, which followed the order 15 degrees C > 5 degrees C > pre-incubated. Incubation temperature, soil layer and their interaction have significant effects on bacterial alpha diversity (Chao index). Bacterial communities under different temperature were clearly distinguished. Chloroflexi, Actinobacteria, Proteobacteria, and Acidobacteria accounted for more than 80% of the community abundance at the phylum level. Warming decreased the relative abundance of Chloroflexi and Acidobacteria, while Actinobacteria and Proteobacteria exhibited increasing trend. At family level, the abundance of norank_o__norank_c__AD3 and Ktedonobacteraceae decreased significantly with the increase of temperature, while Micrococcaccac increased. In addition, the amount of SOC mineralization were positively correlated with the relative abundances of most bacterial phyla and SOC content. SOC content was positively correlated with the relative abundance of most bacterial phyla. Results indicate that the SOC content was the primary explanatory variable and driver of microbial regulation for SOC mineralization. Our results provide a new perspective for understanding the microbial mechanisms that accelerates SOC decomposition under warming conditions in the forest-wetland ecotone of permafrost region.

Anthropogenic aerosols (AAs) induce global and regional tropospheric circulation adjustments due to the radiative energy perturbations. The overall cooling effects of AA, which mask a portion of global warming, have been the subject of many studies but still have large uncertainty. The interhemispheric contrast in AA forcing has also been demonstrated to induce a major shift in atmospheric circulation. However, the zonal redistribution of AA emissions since start of the 20th century, with a notable decline in the Western Hemisphere (North America and Europe) and a continuous increase in the Eastern Hemisphere (South Asia and East Asia), has received less attention. Here we utilize four sets of single-model initial-condition large-ensemble simulations with various combinations of external forcings to quantify the radiative and circulation responses due to the spatial redistribution of AA forcing during 1980-2020. In particular, we focus on the distinct climate responses due to fossil-fuel-related (FF) aerosols emitted from the Western Hemisphere (WH) versus the Eastern Hemisphere (EH). The zonal (west to east) redistribution of FF aerosol emission since the 1980s leads to a weakening negative radiative forcing over the WH mid-to-high latitudes and an enhancing negative radiative forcing over the EH at lower latitudes. Overall, the FF aerosol leads to a northward shift of the Hadley cell and an equatorward shift of the Northern Hemisphere (NH) jet stream. Here, two sets of regional FF simulations (Fix_EastFF1920 and Fix_WestFF1920) are performed to separate the roles of zonally asymmetric aerosol forcings. We find that the WH aerosol forcing, located in the extratropics, dominates the northward shift of the Hadley cell by inducing an interhemispheric imbalance in radiative forcing. On the other hand, the EH aerosol forcing, located closer to the tropics, dominates the equatorward shift of the NH jet stream. The consistent relationship between the jet stream shift and the top-of-atmosphere net solar flux (FSNTOA) gradient suggests that the latter serves as a rule-of-thumb guidance for the expected shift of the NH jet stream. The surface effect of EH aerosol forcing (mainly from low- to midlatitudes) is confined more locally and only induces weak warming over the northeastern Pacific and North Atlantic. In contrast, the WH aerosol reduction leads to a large-scale warming over NH mid-to-high latitudes that largely offsets the cooling over the northeastern Pacific due to EH aerosols. The simulated competing roles of regional aerosol forcings in driving atmospheric circulation and surface temperature responses during the recent decades highlight the importance of considering zonally asymmetric forcings (west to east) and also their meridional locations within the NH (tropical vs. extratropical).