Over most northern regions, break-up is primarily a spring event. Historical evidence, however, has shown that the timing of river-ice break-up has been shifting in many areas of the Northern Hemisphere and these shifts were associated with observed air temperatures during the break-up period. This paper reviews past trends in break-up from the Eurasian and North American circumpolar regions and synthesizes them into a regional and temporal context. It also evaluates various hydro-climatic explanations for these trends including associations with winter/spring air temperature variations and relationships to large-scale circulation patterns. Even more dramatic changes to break-up timing and magnitude are forecast to occur as the result of climate change. Insights toward future break-up conditions are discussed for two broad-scale regions: the North, a region forecast to experience the most pronounced warming, and the southern limit of the cold regions, a zone of particular cryospheric sensitivity to warming.

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