The vulnerability and resilience of continuous permafrost systems to climate change

尽管北极气候出现了有据可查的变暖趋势，永久冻土温度也相应上升，但北极高永久冻土系统对气候变化的反应仍然存在极大的不确定性。一些基于模型的研究表明，普遍存在地形不稳定、永久冻土融化和消失，而其他基于实地的研究表明，永久冻土系统可能比模拟情景所暗示的更具弹性。对永久冻土对气候变化的响应进行概括，可能会导致对碳通量和地貌变化的估计错误。为了更好地约束现有模型，迫切需要对活动层和多年冻土上部的热湿通量进行经验观测。目前的提案侧重于埃尔斯米尔岛、阿克塞尔海贝格岛和赫谢尔群岛上的主要高北极永久冻土系统对气候变化的脆弱性，办法是侧重于活动层、活动层永久冻土界面、冰楔系统、被大量地面冰覆盖的地貌和短暂表面冰区中的热力学过程。通过详细测量边界层气候、地表温度、通过活动层进入永冻层的温度、通过活动层和永冻层的质量和能量通量，再加上对一系列地质生态系统(冰楔、湿地、冰芯表面、极地沙漠和冻土带)的季节性积雪深度和分布模式、植被和小尺度地形变化的观测，将有助于更好地理解气候输入与多年冻土反应之间的动态关系。一旦大范围的热岩溶开始，永久冻土系统就会变得高度不稳定。热岩溶的渐进性导致了很长一段时间(几十年)的地形不稳定，这将影响到几乎所有北方活动(交通、社区基础设施、资源开发)。这些变化将对加拿大产生深远的影响，作为一个北部国家，大约50%的面积被永久冻土覆盖，我们需要站在永久冻土脆弱性研究的前沿。

Despite a well-documented warming trend in Arctic climate and a corresponding increase in permafrost temperatures there remains tremendous uncertainty about the response of high Arctic permafrost systems to climate change. Several model-based studies suggest widespread terrain instability, melting and disappearance of permafrost, while other field-based studies indicate that permafrost systems may be more resilient than modeling scenarios imply. Generalizations concerning permafrost response to climate change can result in errors in estimates of carbon fluxes and landscape change. There is an urgent need for empirical observation of heat and moisture fluxes for the active layer and the upper part of permafrost to better constrain current models. The current proposal focuses on the vulnerability of key high Arctic permafrost systems on Ellesmere, Axel Heiberg and Herschel Islands to climate change by focusing on thermodynamic processes in the active layer, at the active layer permafrost interface, in ice wedge systems, landscapes underlain by massive ground ice and areas of ephemeral surface ice. By making detailed measurements of boundary layer climate, surface temperature, temperatures through the active layer into permafrost, and mass and energy fluxes through the active layer and at the permafrost table coupled with observations on seasonal snow depth and distribution patterns, vegetation and small scale topographic changes for a range of geo-ecosystems (ice wedges, wet lands, ice-cored surfaces, polar desert and tundra) will contribute a better understanding about the dynamic relationship between climate inputs and permafrost response. Once widespread thermokarst begins permafrost systems become highly unstable. The progressive nature of thermokarst results in very long periods (decades) of terrain instability that will affect virtually all northern activities (transportation, community infrastructure, resource development. These changes will have a profound impact on Canada, as a northern nation with roughly 50% of it area underlain by permafrost we need to be at the forefront of research on permafrost vulnerability.