The vulnerability and resilience of continuous permafrost systems to climate change

尽管北极气候变暖的趋势和永久冻土温度的相应增加有据可查，但北极高永久冻土系统对气候变化的反应仍然存在巨大的不确定性。一些基于模型的研究表明，广泛的地形不稳定，融化和永久冻土消失，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。关于永久冻土对气候变化的反应的概括可能会导致碳通量和景观变化估计的错误。迫切需要对活动层和冻土上部的热湿通量进行经验观测，以更好地约束当前的模型。目前的建议侧重于埃尔斯米尔、阿克塞尔海伯格和赫歇尔群岛的主要高纬度北极永久冻土系统对气候变化的脆弱性，重点是活动层、活动层永久冻土界面、冰楔系统、大量地面冰和短暂表面冰地区的地貌的热力学过程。通过对边界层气候、地表温度、通过活动层进入永久冻土层的温度、通过活动层和永久冻土层的物质和能量通量进行详细测量，并结合对一系列地质生态系统的季节性雪深和分布模式、植被和小规模地形变化的观测，（冰楔、湿地、冰芯表面、极地沙漠和苔原）将有助于更好地了解气候输入与永久冻土响应之间的动态关系。一旦广泛的热岩溶开始，永久冻土系统变得非常不稳定。热岩溶的渐进性质导致很长时期（几十年）的地形不稳定，这将影响几乎所有北方活动（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，作为一个北方国家，大约50%的土地被永久冻土覆盖，我们需要站在永久冻土脆弱性研究的最前沿。

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.