Earth's portfolio of extreme sediment transport events
Earth's portfolio of extreme sediment transport events
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DOI：
10.1016/j.earscirev.2012.02.006
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发表时间：
2012-05
影响因子：
12.1
通讯作者：
O. Korup
中科院分区：
文献类型：
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作者：
O. Korup
对沉积物通量和沉积物从山坡到河流、河口、三角洲、大陆架和深海盆地的全球循环的定量估计有着悠久的研究传统。在这方面，迄今为止，对极为罕见的特大型泥沙输运事件一直没有进行系统分析。为了填补这一知识空白，我回顾了火山爆发、地震和风暴引发的滑坡事件以及灾难性的溃坝事件影响下的山区河流中报告的最高沉积量。极端比产量，这里定义为超过汇编数据的第95百分位数，如果在1年内平均，则为~ 104 tkm − 2 yr − 1。这些极端产量相差八个数量级，但系统地衰减与参考间隔从几分钟到几千年，使产量变化三个数量级为一个给定的参考间隔。在给定的参考区间内，来自自然溃坝和火山碎屑喷发的沉积物输送在这些产量中占主导地位。即使平均超过102- 103年，个别干扰的贡献可能仍然高于相应的流域剥蚀率。我进一步估计个别巨型陆地和海底质量运动的沉积物（再）动员率。不到50次冰后期海底物质运动涉及相当于当代全球河流沉积物到地球海洋的年流量的10%，而个别事件的动员率与台湾或新西兰等构造活动造山带的十年尺度沉积物排放量相当。与灾难性的自然溃坝相关联的沉积物冲刷是不稳定的，并在末次冰期-间冰期过渡期显示出明显的扭结，这是由于非常大的晚更新世冰缘湖的排水。除了强调高量级和低频率事件对全球沉积物级联的贡献外，这些研究结果还强调了沉积物储存对燃料的重要性，而不是缓冲高沉积物输运率。
Quantitative estimates of sediment flux and the global cycling of sediments from hillslopes to rivers, estuaries, deltas, continental shelves, and deep-sea basins have a long research tradition. In this context, extremely large and commensurately rare sediment transport events have so far eluded a systematic analysis. To start filling this knowledge gap I review some of the highest reported sediment yields in mountain rivers impacted by volcanic eruptions, earthquake- and storm-triggered landslide episodes, and catastrophic dam breaks. Extreme specific yields, defined here as those exceeding the 95th percentile of compiled data, are ~104tkm−2yr−1if averaged over 1yr. These extreme yields vary by eight orders of magnitude, but systematically decay with reference intervals from minutes to millennia such that yields vary by three orders of magnitude for a given reference interval. Sediment delivery from natural dam breaks and pyroclastic eruptions dominate these yields for a given reference interval. Even if averaged over 102–103yr, the contribution of individual disturbances may remain elevated above corresponding catchment denudation rates. I further estimate rates of sediment (re-)mobilisation by individual giant terrestrial and submarine mass movements. Less than 50 postglacial submarine mass movements have involved an equivalent of ~10% of the contemporary annual global flux of fluvial sediment to Earth's oceans, while mobilisation rates by individual events rival the decadal-scale sediment discharge from tectonically active orogens such as Taiwan or New Zealand. Sediment flushing associated with catastrophic natural dam breaks is non-stationary and shows a distinct kink at the last glacial-interglacial transition, owing to the drainage of very large late Pleistocene ice-marginal lakes. Besides emphasising the contribution of high-magnitude and low-frequency events to the global sediment cascade, these findings stress the importance of sediment storage for fuelling rather than buffering high sediment transport rates.