Spatial and Temporal Influences of Thermokarst Failures on Surface Processes in Arctic Landscapes

Recent summaries of international research clearly document the past and future extent of climate warming in the Arctic. These summaries suggest that in the future, rising temperatures will be accompanied by increased precipitation, mostly as rain: 20% more over the Arctic as a whole and up to 30% more in coastal areas during the winter and autumn. These climate changes will have important impacts on Arctic Systems. Of direct interest to this research is the likelihood that warming will promote permafrost degradation and thaw. Formerly frozen soils may be further destabilized by increased precipitation, leading to hillslope thermokarst failures. Recent work has documented that thermokarst failures are abundant and appear to have become more numerous around Toolik Lake on the eastern North Slope and in the western Noatak River basin in Alaska. A widespread and long-term increase in the incidence of thermokarst failures may have important impacts on the structure and function of arctic headwater landscapes. This research will use a systems approach to address hypotheses about how thermokarst failures influence the structure and function of the arctic landscape. It will focus on the composition of vegetation, the distribution and processing of soil nutrients, and exports of sediments and nutrients to stream and lake ecosystems. Results obtained at this hillslope scale will be linked to patterns observed at the landscape scale to test hypotheses about the spatial distribution of thermokarst failures in the arctic foothills. It is important to understand these interactions because perhaps the greatest potential impacts of changing land surface processes and formation of thermokarst failures are feedbacks to the climate system through energy, albedo, water, and trace gas exchange. This research is designed to quantify linkages among climatology, hillslope hydrology, geomorphology, geocryology, community ecology of vegetation, soil nutrient dynamics, microbial ecology, trace gas dynamics, and aquatic ecology. It will employ a combination of field experimentation, remote sensing, and simulation modeling as a means to quantify these relationships.国际学界近期发表的综述研究清晰记录了北极地区气候变暖的历史进程与未来影响范围。此类综述指出，未来气温上升将伴随降水总量增加，且降水形式将以降雨为主：整个北极地区的降水量将提升20%，冬季与秋季的沿海区域降水量增幅可达30%。此类气候变化将对北极系统造成重要影响。本研究的核心关注点之一为：气候变暖可能会加剧多年冻土退化（permafrost degradation）与解冻。此前处于永久冻结状态的土壤可能因降水增加进一步失稳，进而引发山坡热融滑塌（hillslope thermokarst failures）。近期研究已证实，热融滑塌现象分布广泛，且在阿拉斯加北坡东部的图利克湖（Toolik Lake）周边与西部的诺阿塔克河流域（Noatak River basin）内，此类滑塌的数量似乎有所增多。热融滑塌发生率的大范围长期增长，可能会对北极源头景观的结构与功能产生显著影响。本研究将采用系统方法（systems approach），围绕热融滑塌如何影响北极景观的结构与功能这一科学问题验证相关假说。研究将聚焦于植被组成、土壤养分的分布与转化过程，以及沉积物与养分向溪流及湖泊生态系统的输出情况。本研究将把山坡尺度下获取的研究结果，与景观尺度下观测到的分布模式相结合，以验证关于北极山麓（arctic foothills）内热融滑塌空间分布的相关假说。理解此类相互作用至关重要，因为地表过程变化与热融滑塌形成可能带来的最大潜在影响，是通过能量、反照率（albedo）、水分与痕量气体交换（trace gas exchange）对气候系统产生反馈。本研究旨在量化气候学（climatology）、山坡水文学（hillslope hydrology）、地貌学（geomorphology）、冻土学（geocryology）、植被群落生态学、土壤养分动态、微生物生态学、痕量气体动态与水生生态学之间的关联。研究将结合野外实验、遥感（remote sensing）与模拟建模（simulation modeling）等手段，对上述关联进行量化分析。