Complexities in barrier island response to sea level rise: Insights from numerical model experiments, North Carolina Outer Banks
Complexities in barrier island response to sea level rise: Insights from numerical model experiments, North Carolina Outer Banks
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DOI：
10.1029/2009jf001299
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发表时间：
2010-07-09
影响因子：
3.9
通讯作者：
Stolper, David
中科院分区：
文献类型：
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作者：
Moore, Laura J.;List, Jeffrey H.;Stolper, David
利用形态-行为模型进行敏感性实验，我们调查了海平面上升的复杂的沿海环境的各种因素的变化的响应。实验表明，衬底组成，其次是衬底坡度，海平面上升速率，和沉积物供应率的排名顺序，是最重要的因素，在确定障壁岛响应海平面上升。我们发现，地貌阈值跨越，定义为状态的变化（e。例如，在一个实施例中，从向陆地迁移到溺水），这是不可逆转的十年到千年的时间尺度，是最有可能发生在泥泞的海岸系统，在那里的组合衬底的组成，深度依赖的限制滨面响应率，和衬底的可侵蚀性可能会阻止沙子被释放足够快，或足够的数量，以保持陆上屏障。分析表明，影响沉积物可用性的因素，如低基质砂比例和高沉积物流失率，导致障碍迁移向陆地沿着的轨迹具有较低的斜率比平均障碍岛坡度，从而定义了一个“有效的”障碍岛坡度。在其他因素相同的情况下，此类屏障往往较小，且与更深的下切滨面相关，因此，与较大、下切较少的屏障相比，每增加一个海平面，需要较少的迁移来释放足够的沙子以维持陆上暴露。因此，较大/较少切割的屏障的演变更可能受到滨面侵蚀速率或基底可蚀性的限制，使其比较小/较多切割的屏障更容易因海平面上升速率增加而解体。因此，小/深切的北卡罗来纳州障碍可能会持续在短期内（虽然他们的长期命运是不太确定的，因为低衬底斜坡，很快就会遇到）。总的来说，结果表明了系统历史的重要性（e。例如，在一个实施例中，以前的坡度、沉积物预算等）在确定迁移轨迹，从而如何屏障岛将应对海平面上升。虽然简单的分析计算可以预测简化的沿海环境中的屏障响应（例如，例如，在一个实施例中，恒定斜率、恒定海平面上升速率等），我们的模型实验表明，形态-行为建模对于提供关于在具有复杂几何形状的环境中可能发生的变化的关键见解是必要的，特别是当多个参数同时变化时。
Using a morphological-behavior model to conduct sensitivity experiments, we investigate the sea level rise response of a complex coastal environment to changes in a variety of factors. Experiments reveal that substrate composition, followed in rank order by substrate slope, sea level rise rate, and sediment supply rate, are the most important factors in determining barrier island response to sea level rise. We find that geomorphic threshold crossing, defined as a change in state (e. g., from landward migrating to drowning) that is irreversible over decadal to millennial time scales, is most likely to occur in muddy coastal systems where the combination of substrate composition, depth-dependent limitations on shoreface response rates, and substrate erodibility may prevent sand from being liberated rapidly enough, or in sufficient quantity, to maintain a subaerial barrier. Analyses indicate that factors affecting sediment availability such as low substrate sand proportions and high sediment loss rates cause a barrier to migrate landward along a trajectory having a lower slope than average barrier island slope, thereby defining an "effective" barrier island slope. Other factors being equal, such barriers will tend to be smaller and associated with a more deeply incised shoreface, thereby requiring less migration per sea level rise increment to liberate sufficient sand to maintain subaerial exposure than larger, less incised barriers. As a result, the evolution of larger/less incised barriers is more likely to be limited by shoreface erosion rates or substrate erodibility making them more prone to disintegration related to increasing sea level rise rates than smaller/more incised barriers. Thus, the small/deeply incised North Carolina barriers are likely to persist in the near term (although their long-term fate is less certain because of the low substrate slopes that will soon be encountered). In aggregate, results point to the importance of system history (e. g., previous slopes, sediment budgets, etc.) in determining migration trajectories and therefore how a barrier island will respond to sea level rise. Although simple analytical calculations may predict barrier response in simplified coastal environments (e. g., constant slope, constant sea level rise rate, etc.), our model experiments demonstrate that morphological-behavior modeling is necessary to provide critical insights regarding changes that may occur in environments having complex geometries, especially when multiple parameters change simultaneously.