Extreme events, trends, and variability in Northern Hemisphere lake-ice phenology (1855-2005)
Extreme events, trends, and variability in Northern Hemisphere lake-ice phenology (1855-2005)
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DOI：
10.1007/s10584-011-0212-8
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发表时间：
2012-05-01
期刊：
影响因子：
4.8
通讯作者：
Granin, Nick G.
中科院分区：
文献类型：
--
作者：
Benson, Barbara J.;Magnuson, John J.;Granin, Nick G.
极端事件对环境和人类福祉的影响往往比平均条件的变化更大。在这里，我们研究了北半球湖泊冰每年形成和消失的时间中极端事件发生的变化。平均条件的变化和平均条件周围变率的变化都可以改变极端事件的概率。利用1855-6年至2004-5年和1905-6年至2004-5年两个时期的75个湖泊的长期冰物候资料，在了解极端事件发生的背景下，研究了长期趋势和变异模式。我们还研究了100年数据集的30年子集（1975- 5至2004-5）的趋势模式。最近30年期间冰变量的趋势比100年和150年期间的趋势更陡峭，150年期间的趋势比100年期间的趋势更陡峭。基于线性回归的各时间段的变化率（每十年的天数）范围为冻结晚0.3-1.6天，破裂早0.5-1.9天，持续时间短0.7-4.3天。大多数情况下，标准差在150年和100年期间没有变化，或者下降。在最近50年期间，所有冰测量在10年窗口计算的标准差都增加了。在150年和100年期间，平均冰期的变化而不是变率的变化对与较暖条件相关的极端湖冰事件频率的显著增加和与较冷条件相关的极端事件频率的减少影响最大。
Often extreme events, more than changes in mean conditions, have the greatest impact on the environment and human well-being. Here we examine changes in the occurrence of extremes in the timing of the annual formation and disappearance of lake ice in the Northern Hemisphere. Both changes in the mean condition and in variability around the mean condition can alter the probability of extreme events. Using long-term ice phenology data covering two periods 1855-6 to 2004-5 and 1905-6 to 2004-5 for a total of 75 lakes, we examined patterns in long-term trends and variability in the context of understanding the occurrence of extreme events. We also examined patterns in trends for a 30-year subset (1975-6 to 2004-5) of the 100-year data set. Trends for ice variables in the recent 30-year period were steeper than those in the 100- and 150-year periods, and trends in the 150-year period were steeper than in the 100-year period. Ranges of rates of change (days per decade) among time periods based on linear regression were 0.3-1.6 later for freeze, 0.5-1.9 earlier for breakup, and 0.7-4.3 shorter for duration. Mostly, standard deviation did not change, or it decreased in the 150-year and 100-year periods. During the recent 50-year period, standard deviation calculated in 10-year windows increased for all ice measures. For the 150-year and 100-year periods changes in the mean ice dates rather than changes in variability most strongly influenced the significant increases in the frequency of extreme lake ice events associated with warmer conditions and decreases in the frequency of extreme events associated with cooler conditions.