Permafrost limnoscapes: Critical places at critical times

加拿大一半领土上存在永久冻土，北半球覆盖面积超过2000万平方公里。它是北方生态系统和基础设施的基础。由于最近的气候变化，北极地区的气候变化速度是全球其他地区的两倍，永久冻土的稳定性正受到威胁。其普遍融化(例如，土壤侵蚀和下沉)对自然和人类系统的潜在影响可能是渐进的和灾难性的。此外，由于北方的冻土含有大量的有机碳，由富含冰的永久冻土(所谓的“热岩溶”湖)融化形成的水生系统可被视为生物地球化学“热点”，向大气排放温室气体，从而放大气温升高。我的研究旨在描述气候引起的永久冻土退化对整个北极自然和人类景观的影响。我探索了不同的空间和时间尺度，特别关注水生生态系统的动态。对于这个探索计划，我将沿着三个研究轴线，沿着“景观连续体”(土壤-水-沉积物-气体)、实验室分析和地学工具(例如遥感)整合实地工作采样：1)描述控制冻融循环和热岩溶开始的北极土壤的地球物理性质；2)将实地测量与航空红外成像相结合，量化富含湖泊的永久冻土景观或“湖泊景观”的温室气体排放；3)根据沉积物岩心分析，重建过去影响北部湖泊盆地的关键环境变化(例如，碳积累、湖泊水位下降和干燥)。为了更好地了解这些复杂过程中的空间差异，我的程序部署在加拿大北部的三个研究地点：剑桥湾和比洛特岛、努纳武特(北极连续永久冻土)和马尼托巴省丘吉尔附近的哈德逊湾西部低地(亚北极地区的连续-不连续永久冻土边界，位于世界第二大泥炭地带)。我的研究项目还旨在培训下一代寒冷地区的科学家，无论是在实地还是在实验室/办公室，他们都是与加拿大北部社区合作的国际领导者。北极地区未来将成为全球碳源还是碳汇的广泛问题--北极的绿化和/或褐化？--是一个及时的科学和社会问题。目前，模拟多年冻土区未来碳汇和碳源的地球系统模型只包括逐步和广泛的融化(作为“自上而下”的过程)，但不包括局部和突然的扰动。我的综合、实地密集型(“自下而上”)研究计划将有助于用可靠的数据改进这些模型，从而指导将影响北极未来状况和全球气候的缓解决策。

Permafrost is present in half of Canada's territory and covers more than 20 million km2 in the northern hemisphere. It is the foundation of northern ecosystems and infrastructure. Because of recent climate change, which has been twice as rapid across the Arctic compared to elsewhere around the globe, permafrost stability is under threat. Potential impacts of its widespread thaw (e.g., soil erosion and subsidence) could be both progressive and catastrophic on natural and human systems. Moreover, because frozen soils in the North contain great amounts of organic carbon, aquatic systems formed by the thawing of ice-rich permafrost (so-called `thermokarst' lakes) can be considered as biogeochemical `hotspots', emitting greenhouse gases (GHGs) to the atmosphere and thus amplifying temperature increases. My research aims to characterize the impacts of climate-induced permafrost degradation on natural and human landscapes across the Arctic. I explore different spatial and temporal scales, with a special focus on the dynamics of aquatic ecosystems. For this Discovery program I will integrate fieldwork sampling along a `landscape continuum' (soil-water-sediments-gases), laboratory analyses, and geomatic tools (e.g., remote sensing) along three research axes: 1) characterizing the geophysical properties of Arctic soils that control freeze-thaw cycles and thermokarst inception; 2) quantifying GHG emissions from lake-rich permafrost landscapes or `limnoscapes', combining field measurements with airborne infrared imagery; 3) reconstructing past environmental critical changes that have affected northern lacustrine basins (e.g., carbon accumulation, lake level drawdown and desiccation) based on sediment core analysis. To better understand the spatial variations in these complex processes, my program is deployed at three study sites across the Canadian North: Cambridge Bay and Bylot Island, Nunavut (continuous permafrost in the Arctic), and western Hudson Bay Lowlands near Churchill, Manitoba (continuous-discontinuous permafrost boundary in the subarctic zone, in the world's second largest peatland area). My research program also aims at training the next generation of cold-region scientists, both in the field and in the lab/office space, acting as international leaders collaborating with northern communities across Canada. The broad question of whether the Arctic region will act as a global carbon source or sink in the future - greening and/or browning of the Arctic? - is a timely scientific and societal issue. Currently, Earth system models simulating future carbon sinks and sources in permafrost regions only include gradual and widespread thaw (as a `top-down' process), but do not include localized and abrupt disturbances. My integrated, field-intensive (`bottom-up') research program will help to improve such models with reliable data, thereby guiding mitigation decisions that will impact the future state of the Arctic and the global climate.