Drowning of the Mississippi Delta due to insufficient sediment supply and global sea-level rise
Drowning of the Mississippi Delta due to insufficient sediment supply and global sea-level rise
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DOI：
10.1038/ngeo553
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发表时间：
2009-07-01
影响因子：
18.3
通讯作者：
Roberts, Harry H.
中科院分区：
文献类型：
--
作者：
Blum, Michael D.;Roberts, Harry H.
在过去的几个世纪里，与密西西比三角洲有关的三角洲湿地中有25%已经消失在海洋中（1）。保护和恢复海岸的计划要求对密西西比河及其相关沉积物进行改道，以维持和建设新的土地（2，3）。然而，通过在密西西比盆地修建大坝，密西西比河的泥沙量减少了50%，这可能会影响引水计划的有效性（4-6）。在这里，我们计算的沉积物存储在三角洲平原在过去的12,000年，并发现，平均存储率所需的建设洪泛平原和三角洲在此期间超过现代密西西比河泥沙负荷。我们估计，在没有沉积物输入的情况下，到2100年，由于沉降和海平面上升，将有10，000 - 13，500平方公里被淹没。维持现有的三角洲表面积将需要180 - 240亿吨沉积物，这远远超过了目前状态下从密西西比河中汲取的沉积物。我们的结论是，即使沉积物负荷恢复，显著的溺水是不可避免的，因为海平面现在上升的速度至少是三角洲平原建设期间的三倍。
Over the past few centuries, 25% of the deltaic wetlands associated with the Mississippi Delta have been lost to the ocean(1). Plans to protect and restore the coast call for diversions of the Mississippi River, and its associated sediment, to sustain and build new land(2,3). However, the sediment load of the Mississippi River has been reduced by 50% through dam construction in the Mississippi Basin, which could affect the effectiveness of diversion plans(4-6). Here we calculate the amount of sediment stored on the delta plain for the past 12,000 years, and find that mean storage rates necessary to construct the flood plain and delta over this period exceed modern Mississippi River sediment loads. We estimate that, in the absence of sediment input, an additional 10,000-13,500 km(2) will be submerged by the year 2100 owing to subsidence and sea-level rise. Sustaining existing delta surface area would require 18-24 billion tons of sediment, which is significantly more than can be drawn from the Mississippi River in its current state. We conclude that significant drowning is inevitable, even if sediment loads are restored, because sea level is now rising at least three times faster than during delta-plain construction.