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地区的永久冻土迅速退化，对整个生态系统产生连锁影响。这项工作的重点是一种特殊类型的永久冻土退化，涉及地下隧道的形成，这些隧道可以在重新冻结或坍塌之前持续多年。这些隧道的存在被偶然地记录了下来，但它们很难用航空摄影等传统方法探测到，所以它们仍然没有得到充分的研究。先前在阿拉斯加北极地区的研究发现，狼獾在冬天使用这些隧道作为休息和繁殖的洞穴。这项研究通过定位额外的隧道来研究狼獾对这些结构的使用，以了解狼獾和其他北极动物如何使用这些洞穴，以及它们如何影响当地的永久冻土和雪况。虽然多年冻土隧道被认为是热侵蚀沟发展的偶然前兆，但隧道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。冬季持续存在的隧道可能会在重要方面改变永久冻土退化的影响，因为越冬隧道除了为休息、筑巢或冬眠的野生动物提供结构性栖息地外，还可能改变活动层和积雪的局部热状态。本研究探讨了越冬隧道和洞穴系统如何影响北极系统的各种生态组成部分。具体来说，项目团队评估了以下假设：冬季洞穴(1)为北极哺乳动物群落的多种物种提供结构和热保护；(2)改变冬季近地表（即洞穴顶部）的温度和湿度；(3)通过改变通过积雪的蒸汽通量，降低了上覆积雪的质量，使其成为海底哺乳动物的栖息地。研究小组通过(1)获取冬季GPS项圈数据、野生动物足迹和洞穴运动激活相机的照片，并将洞穴中的温度和湿度与其他形式的结构性栖息地进行比较，(2)测量洞穴和控制地点的土壤温度、土壤湿度和物理雪特性，以及(3)通过巢穴调查记录上覆苔原和控制地点的小型哺乳动物的冬季活动。该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全生态系统影响的理解。该项目包括访问北极社区，讨论研究结果，接收社区代表的反馈，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所看到的变化的影响。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值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.