Climate change/variability and freshwater-ice systems

淡水冰是寒冷地区湖泊和河流的重要组成部分，是相关生物、化学和物理过程的重要调节剂。尽管人们对气候变化对冰雪覆盖系统的影响表示了严重关切（例如，政府间气候变化专门委员会最近的评估和北极气候影响评估），但对这类系统的了解相对薄弱，因此难以预测气候变化影响的性质。该项目将重点填补我们的一些最重要的知识空白，通过解决三个研究领域：极端水文事件；气候控制;以及对水文生态系统的影响。极端水文事件的焦点将是河冰破裂和相关的冰堵塞。这些事件可能会产生超过在开放水域期间类似流量下可能产生的洪水。虽然已知崩解洪水会造成重大的经济损失，而且对水生系统的环境健康也至关重要，但尚未对其重要性进行大规模评估。本研究将通过对历史上破碎洪水的频率和规模进行全国和极地评估，并将结果与开放水域时期的结果进行比较，来填补这一空白。这将为改善基础设施规划和环境管理提供基础，并为本研究计划的第二个目标奠定基础：预测未来气候变化如何影响此类极端事件的频率和强度。河流和湖泊生态的重大变化，特别是包括水质的变化，预计也将由气候引起的河冰覆盖的变化造成。然而，预估的生态变化主要是基于对冰盖变化的估计，而不是基于基于物理模型的结果。这个项目的最终目标是建立这样的模型，以便我们能够更准确地预测北方水生系统将如何应对气候变化。

Freshwater ice is an integral component of cold-regions lakes and rivers and an important modifier of related biological, chemical and physical processes.   Although serious concerns have been expressed about the impacts of climate change on ice-covered systems (e.g., the recent assessment by the Intergovernmental Panel on Climate Change and the Arctic Climate Impact Assessment), knowledge of such systems is relatively weak making it difficult to predict the nature of the effects of a changing climate.  This project will focus on filling some of our most important knowledge gaps by addressing three research areas: extreme hydrologic events; climatic controls; and effects on hydro-ecological systems.The focus of extreme hydrologic events will be river-ice breakup and associated ice jamming.  Such events can produce floods exceeding those possible under similar flow during the open-water period.  Although breakup flooding is known to produce significant economic damage and also to be critical to the environmental health of aquatic systems, no broad-scale assessment of its importance has been conducted.  This study will fill this gap by conducting a national and circumpolar evaluation of the historical frequency and magnitude of breakup floods and compare the results to those for the open-water period.  This will provide a basis for improved infrastructure planning and environmental management, as well as be the basis for the second objective of this research program: predicting how the frequency and magnitude of such extreme events will be affected by future climate change.   Major changes in river and lake ecology, particularly including the water quality, are also expected to result from climate-induced changes to river-ice cover.  Projected ecological changes, however, have been based primarily on guesstimates of changes in the ice cover, not on the results of physically-based models.  The final objective of this program will be to undertake such modelling so that we can more accurately forecast how northern aquatic systems will respond to climate change.