Doctoral Dissertation Research: Impact of Thermo-erosion Permafrost Tunnels to Physical and Ecological Processes in the Arctic

气候变暖正在推动整个北极的永久冻土迅速退化，并对整个生态系统产生级联影响。这项工作的中心是一种特殊类型的永久冻土退化，涉及地下隧道的形成，这些隧道可能会持续多年，然后重新冻结或坍塌。这些隧道的存在已经被机会主义地记录下来，但它们很难用传统的方法如航空摄影来发现，所以它们仍然没有得到充分的研究。之前在北极阿拉斯加进行的研究发现，狼獾在冬季使用这些隧道作为休息和繁殖的洞穴。这项研究通过设置更多的隧道来检查狼獾对这些结构的使用，以了解这些洞穴是如何被狼獾和其他北极动物使用的，以及它们如何影响当地的冻土和积雪条件。尽管多年冻土隧道工程偶尔被认为是热蚀冲沟形成的前兆，但隧道工程本身对永久冻土退化的物理和生态过程的影响程度仍未得到解决。越冬隧道可能会在重要方面改变永久冻土退化的影响，因为越冬隧道可能会改变活动层和积雪的局部热状况，除了为休息、丹宁或冬眠的野生动物提供结构性栖息地之外。这项研究调查了越冬隧道和洞穴系统如何影响北极系统的各种生态成分。具体地说，项目组评估了以下假设：(1)冬季洞穴为北极哺乳动物群落中的各种物种提供结构和热保护，(2)改变近地表(即洞穴顶部)的冬季温度和湿度，以及(3)通过改变积雪中的水蒸气通量，降低作为底栖哺乳动物栖息地的覆盖积雪的质量。该团队通过(1)获取冬季GPS项圈数据、野生动物踪迹和洞穴运动激活相机拍摄的照片，并将洞穴内的温度和湿度与其他形式的结构栖息地进行比较，(2)测量洞穴和对照地点的土壤温度、土壤水分和物理积雪特性，以及(3)通过筑巢调查记录小型哺乳动物在覆盖的冻土带和对照地点的冬季活动，对这些假说进行了研究。这个项目促进了我们对永久冻土如何退化以及与这种退化相关的整个生态系统的影响的理解。该项目包括访问北极社区，讨论调查结果，听取社区代表的反馈，并加强研究人员与当地土地使用者之间的关系。此外，研究人员访问当地学校并制作教育材料，强调跨学科北极气候变化研究的重要性，以帮助了解当地社区在其环境中看到的变化的影响。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Climate warming is driving rapid permafrost degradation throughout the Arctic, with cascading impacts across the ecosystem. This work centers on a particular type of permafrost degradation, involving the formation of underground tunnels that can persist across multiple years before either refreezing or collapsing. The existence of these tunnels has been documented opportunistically, but they are difficult to detect using traditional methods such as aerial photography, so they remain understudied. Previous research in Arctic Alaska found that wolverines use these tunnels for resting and reproductive dens during winter. This study examines wolverines’ use of these structures by locating additional tunnels to understand how these caves are used by wolverines and other Arctic animals as well as how they impact local permafrost and snow conditions. Although permafrost tunneling is recognized as an occasional precursor to the development of thermo-erosion gullies, the extent to which tunneling per se influences the physical and ecological processes of permafrost degradation remains unaddressed. Tunnels that persist over winter could alter the impacts of permafrost degradation in important ways, since overwinter tunnels likely change the local thermal regime of the active layer and snowpack, in addition to providing structural habitat for resting, denning, or hibernating wildlife. This research investigates how overwintering tunnels and cave systems influence diverse ecological components of the Arctic system. Specifically, the project team evaluates the hypotheses that wintertime caves (1) provide structural and thermal protection for diverse species in the Arctic mammal community, (2) alter wintertime temperature and moisture of the near-surface ground (i.e., the cave roof), and (3) reduce the quality of overlying snowpack as habitat for subnivean mammals by altering vapor flux through the snowpack. The team investigates these hypotheses by (1) obtaining wintertime GPS collar data, wildlife tracks, and photographs from motion-activated cameras at caves, and comparing temperature and humidity in caves to other forms of structural habitat, (2) measuring soil temperature, soil moisture, and physical snow properties at caves and control sites, and (3) recording wintertime activity of small mammals on overlying tundra and control sites through nest surveys. This project advances our understanding of how permafrost degrades, and the ecosystem-wide impacts associated with such degradation. The project involves visits to Arctic communities to discuss findings, receive feedback from community representatives, and strengthen relationships between researchers and local land users. Additionally, researchers visit local schools and produce educational material highlighting the importance of interdisciplinary Arctic climate change research for helping understand the repercussions of the changes local communities are seeing in their environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.