Vulnerability and resilience of continuous permafrost systems to climate change

尽管北极气候的变暖趋势和永久冻土温度的相应升高有充分的证据，但关于连续永久冻土系统对气候变化的响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、永久冻土融化和消失，而最近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响应的概括可能导致对碳通量和景观变化的估计出现错误。为了更好地约束模拟活动，迫切需要对活动层和永久冻土上部的热湿通量进行经验观测。本研究的主要目标是通过关注活动层和活动层永久冻土界面的热力学过程，评估北极关键连续和高纬度永久冻土系统对气候变化的脆弱性。在Ellesmere、Axel Heiberg和Herschel群岛的现场将包括冰楔系统、湿地和冻土带景观的特征，这些景观被地面冰（包括大块冰和冰胶结地面）所覆盖。通过对边界层气候、地表温度、温度、通过活动层和永久冻土层的质量和能量通量的详细测量，再加上对特定地质生态系统的季节性雪深和分布、植被和局部地形变化的观测，本研究将有助于更好地理解气候输入与永久冻土层响应之间的动态关系。通过将永久冻土视为一个复杂的系统，本研究将确定有助于系统弹性和潜在引爆点的各种反馈过程。众所周知，一旦广泛的热岩溶开始，永久冻土系统变得高度不稳定，正常的自我调节过程往往需要几十年才能重新建立一个新的平衡。通过将CO2和CH4通量的测量结果与这些观测结果相结合，本研究不仅确定了变化的阈值，而且确定了气候系统的潜在反馈。

Despite a well-documented warming trend in Arctic climate and a corresponding increase in permafrost temperatures there remains tremendous uncertainty about the response of continuous permafrost systems to climate change. Several model-based studies suggest widespread terrain instability, melting and disappearance of permafrost, while recent field-based studies indicate that permafrost systems may be more resilient than modelling scenarios imply. Generalizations concerning permafrost response to climate change can result in errors in estimates of carbon flux 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 modeling activities. The primary goal of this research is to assessment of the vulnerability of key continuous and high Arctic permafrost systems to climate change by focusing on thermodynamic processes in the active layer and at the active layer permafrost interface. Field sites on Ellesmere, Axel Heiberg and Herschel Islands will include areas characterized by ice wedge systems, wetlands, and tundra landscapes underlain by ground ice (including massive ice and ice cemented ground). By making detailed measurements of boundary layer climate, surface temperature, temperatures, and mass and energy fluxes through the active layer and at the permafrost table coupled with observations on seasonal snow depth and distribution, vegetation, and local topographic changes for specific geo-ecosystems this research will contribute a better understanding about the dynamic relationship between climate inputs and permafrost response. By looking at permafrost as a complex system this study will identify various feedback processes that contribute to system resiliency and potential tipping points. It is well understood that once widespread thermokarst begins permafrost systems become highly unstable and the normal self regulating processes often require decades to re-establish a new equilibrium. By coupling measurements of CO2 and CH4 flux to these observations this study not only defines the thresholds of change but potential feed backs to the climate system.