Permafrost limnoscapes: Critical places at critical times

永久冻土存在于加拿大一半的领土上，覆盖北方2 000多万平方公里。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地球仪其他地区的两倍，永久冻土的稳定性受到威胁。其广泛解冻的潜在影响（例如，土壤侵蚀和沉降）对自然和人类系统既可能是渐进的，也可能是灾难性的。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融化而形成的水生系统（所谓的“热岩溶”湖）可被视为地球化学“热点”，向大气排放温室气体，从而加剧温度上升。我的研究旨在描述气候引起的永久冻土退化对整个北极地区自然和人文景观的影响。我探索不同的空间和时间尺度，特别关注水生生态系统的动态。对于这个发现计划，我将整合野外工作采样沿着“景观连续体”（土壤-水-沉积物-气体），实验室分析和地质工具（例如，遥感）沿着三个研究轴：1）表征控制冻融循环和热岩溶开始的北极土壤的地球物理特性; 2）量化来自湖泊丰富的永久冻土景观或“湖沼景观”的温室气体排放，将实地测量与航空红外成像相结合; 3）重建影响北方湖泊盆地的过去环境关键变化（例如，碳积累、湖平面下降和干化）。为了更好地了解这些复杂过程中的空间变化，我的程序部署在加拿大北部的三个研究地点：剑桥湾和拜洛特岛，努纳武特（北极的连续永久冻土），以及哈德逊湾西部低地附近的丘吉尔，马尼托巴（亚北极区的连续-不连续永久冻土边界，世界第二大泥炭地）。我的研究计划还旨在培养下一代寒冷地区的科学家，无论是在现场还是在实验室/办公室空间，作为国际领导人与加拿大各地的北方社区合作。北极地区在未来是否会成为全球碳源或碳汇--北极的绿化和/或布朗宁--这一广泛的问题？- 是一个及时的科学和社会问题。目前，模拟永久冻土区未来碳汇和碳源的地球系统模型只包括逐渐和广泛的解冻（作为一个“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”）的研究计划将有助于改善这些模型与可靠的数据，从而指导缓解决策，将影响北极和全球气候的未来状态。

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.