The impact of permafrost thaw on hydrologic, thermal, and biotic processes remains uncertain, in part due to limitations in subsurface measurement capabilities. To better understand subsurface processes in thermokarst environments, we collocated geophysical and biogeochemical instruments along a thaw gradient between forested permafrost and collapse-scar bogs at the Alaska Peatland Experiment site near Fairbanks, Alaska. Ambient seismic noise monitoring provided continuous high-temporal resolution measurements of water and ice saturation changes. Maps of seismic velocity change identified areas of large summertime velocity reductions nearest the youngest bog, indicating potential thaw and expansion at the bog margin. These results corresponded well with complementary borehole nuclear magnetic resonance measurements of unfrozen water content with depth, which showed permafrost soils nearest the bog edges contained the largest amount of unfrozen water along the study transect, up to 25% by volume. In situ measurements of methane within permafrost soils revealed high concentrations at these bog-edge locations, up to 30% soil gas. Supra-permafrost talik zones were observed at the bog margins, indicating talik formation and perennial liquid water may drive lateral bog expansion and enhanced permafrost carbon losses preceding thaw. Comparison of seismic monitoring with wintertime surface carbon dioxide fluxes revealed differential responses depending on time and proximity to the bogs, capturing the controlling influence of subsurface water and ice on microbial activity and surficial emissions. This study demonstrates a multidisciplinary approach for gaining new understanding of how subsurface physical properties influence greenhouse gas production, emissions, and thermokarst development.

中文翻译：

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水和冰在接近塌陷的永久冻土中的生物物理作用：来自新地球物理观测的见解

永久冻土融化对水文、热和生物过程的影响仍然不确定，部分原因是地下测量能力的限制。为了更好地了解热岩溶环境中的地下过程，我们在阿拉斯加费尔班克斯附近的阿拉斯加泥炭地试验场沿森林覆盖的永久冻土和塌陷疤痕沼泽之间的解冻梯度配置了地球物理和生物地球化学仪器。环境地震噪声监测提供了对水和冰饱和度变化的连续高时间分辨率测量。地震速度变化图确定了最靠近最年轻沼泽的夏季大幅下降的区域，表明沼泽边缘可能出现解冻和扩张。这些结果与未冻结水含量随深度的互补钻孔核磁共振测量结果非常吻合，这表明最靠近沼泽边缘的永久冻土沿研究断面含有最大量的未冻结水，按体积计算高达 25%。对永久冻土中甲烷的原位测量显示，这些沼泽边缘位置的甲烷浓度很高，高达 30% 的土壤气体。在沼泽边缘观察到超永久冻土带，表明 talik 形成和常年液态水可能会推动沼泽横向扩张，并在解冻前增加多年冻土碳损失。地震监测与冬季地表二氧化碳通量的比较揭示了不同的响应取决于时间和与沼泽的距离，捕捉地下水和冰对微生物活动和地表排放的控制影响。这项研究展示了一种多学科方法，可以重新了解地下物理特性如何影响温室气体的产生、排放和热岩溶发展。