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Investigating the effects of long-term hydro-climatic trends on Midwest ice jam events

机译：调查长期水文气候趋势对中西部冰凌事件的影响

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Ice freezeup, breakup and jamming events on northern rivers can cause extensive flooding, damage infrastructure, impede navigation, and impact stream stability and the environment. Under a changing climate the ice regime will change as well, meaning increased risk and uncertainty for affected areas. The layman's perception is that climate change is causing warming that is reducing the length of the ice season, so there will be less ice and less damaging impacts from river ice. The concept of 'less ice' is supported by studies showing shorter ice-affected seasons. However several studies have found that in temperate regions, the effects of climate trends -increasing temperatures and precipitation - may actually exacerbate problems. In recent years, communities in the Midwest U.S. have experienced long duration ice jam events that have resulted in flooding, damages and evacuations. This study presents a first step in identifying trends in damaging ice events in the Midwest. We analyzed the ice regime of three rivers in the region to determine if trends in the hydro-climatic data support the increasing number of damaging freezeup jams observed in recent years, but no regional pattern in trends related to breakup jams were found. We found statistically increasing trends in discharge and precipitation, with no corresponding increase in winter period temperature, which provide evidence for the change in the ice regime for this region. A hindcasting analysis was used to construct a more complete record of historical ice events. This analysis revealed a statistically significant increase in frequency of freezeup jams for most sites and no regional trend in the frequency of midwinter or spring breakup jams. Some increase in the freezeup jam strength was indicated by an increasing trend in the number of freezing degree days (FDD) in the freezeup jam formation period. Communities need to shift their emergency preparedness for river ice problems from the existing focus on relatively regular, short-acting spring breakups. Future emergency management plans need to prepare to respond to the risk and impact of freezeup jams that, according to this analysis, are increasing in frequency and strength while occurring with less predictability and having longer term effects if they freeze in place.
机译：北部河流的冰冻，破裂和卡塞事件可能导致大量洪水，破坏基础设施，阻碍航行并影响河流的稳定性和环境。在气候变化的情况下，冰层也会发生变化，这意味着受影响地区的风险和不确定性都会增加。外行的看法是，气候变化正在导致变暖，从而缩短了冰季的持续时间，因此，冰将减少，河冰的破坏性影响也将减小。研究表明受冰期较短的研究支持了“少冰”的概念。但是，一些研究发现，在温带地区，气候趋势的影响-温度和降水的增加-可能实际上加剧了问题。近年来，美国中西部地区的社区经历了长时间的冰堵事件，导致洪水，破坏和疏散。这项研究为确定中西部破坏性冰雪事件的趋势提供了第一步。我们分析了该地区三条河流的冰冻状况，以确定水文气候数据的趋势是否支持近年来观察到的破坏性冻结果酱数量的增加，但未发现与破碎果酱相关的趋势的区域性模式。我们发现排放量和降水量具有统计上的增加趋势，而冬季温度没有相应增加，这为该地区的冰层变化提供了证据。事后分析被用来构建历史冰事件的更完整记录。该分析表明，在大多数地点，冻结果酱的发生频率在统计学上有显着增加，而冬季或春季破裂的发生频率没有区域性趋势。冻结果酱形成期间，冻结度天数（FDD）的增加趋势表明冻结果酱强度有所增加。社区需要将对河冰问题的应急准备从目前的重点转移到相对定期的，短期的春季活动上。未来的应急管理计划需要做好准备，以应对冻结果酱的风险和影响，根据该分析，冻结果酱的频率和强度会增加，而发生的可能性较小，如果冻结到位，则可预测性较低，并且具有较长期的影响。

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