Geomorphological records of extreme floods and their relationship to decadal-scale climate change
Geomorphological records of extreme floods and their relationship to decadal-scale climate change
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DOI：
10.1016/j.geomorph.2014.04.003
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发表时间：
2014-07
期刊：
影响因子：
3.9
通讯作者：
S. Foulds;H. Griffiths;M. Macklin;P. Brewer
中科院分区：
文献类型：
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作者：
S. Foulds;H. Griffiths;M. Macklin;P. Brewer
在陡峭的高地集水区，极端的降雨和洪水事件会以巨石护堤、碎石锥和冲积扇的形式留下它们发生的地貌痕迹。限制这些功能的年龄是至关重要的理解（一）景观演化响应过去，现在和未来的气候变化;（二）极端的，未测量的洪水在小高地集水区的震级频率。这项研究的重点是英国威尔士的寒武纪山脉，地貌特征和古水文重建的地衣测年与气候数据和文献洪水记录相结合。我们来自威尔士的新数据突出了1900年至1960年之间独特的洪水丰富时期，类似于英国许多其他地衣记录。然而，这项研究揭示了在小流域的高地洪水的基本气候控制新的光。虽然洪水可能发生在任何季节，其时间最好的解释是夏季北大西洋涛动（SNAO）和负（比平均条件更潮湿，有规律的气旋流和洪水）和正阶段（比平均条件更干燥，不太频繁的气旋流和洪水）之间的变化，从个别夏季到十年和几十年的周期。最近潮湿的夏季天气，洪水，和巨石护堤沉积在英国（2007-2012年）是一个明显的负相位移的SNAO。还有越来越多的证据表明，中纬度地区最近夏季的极端天气可能与北极扩大和海冰迅速丧失有关。如果是这种情况，持续和未来的气候变化可能意味着（i）异常天气模式变得更加频繁;（ii）英国高地集水区将经历更高的洪水风险和重大的地貌变化。
Extreme rainfall and flood events in steep upland catchments leave geomorphological traces of their occurrence in the form of boulder berms, debris cones, and alluvial fans. Constraining the age of these features is critical to understanding (i) landscape evolution in response to past, present, and future climate changes; and (ii) the magnitude–frequency of extreme, ungauged floods in small upland catchments. This research focuses on the Cambrian Mountains of Wales, UK, where lichenometric dating of geomorphological features and palaeohydrological reconstructions is combined with climatological data and documentary flood records. Our new data from Wales highlight a distinct flood-rich period between 1900 and 1960, similar to many other UK lichen-dated records. However, this study sheds new light on the underlying climatic controls on upland flooding in small catchments. Although floods can occur in any season, their timing is best explained by the Summer North Atlantic Oscillation (SNAO) and shifts between negative (wetter than average conditions with regular cyclonic flow and flooding) and positive phases (drier than average conditions with less frequent cyclonic flow and flooding), which vary from individual summers to decadal and multidecadal periods. Recent wet summer weather, flooding, and boulder-berm deposition in the UK (2007–2012) are related to a pronounced negative phase shift of the SNAO. There is also increasing evidence that recent summer weather extremes in the mid-latitudes may be related to Arctic amplification and rapid sea ice loss. If this is the case, continuing and future climate change is likely to mean that (i) unusual weather patterns become more frequent; and (ii) upland UK catchments will experience heightened flood risk and significant geomorphological changes.