Abstract Low-lying coral reef islands will be significantly impacted by future sea-level rise (SLR). It is generally expected that SLR will destabilise reef islands because increasing reef submergence allows larger waves, and therefore greater energy transmission, across reef flats. However, the potential impacts of SLR on reef flat sediment transport and sediment delivery to island shorelines are poorly understood. Here, we use the currents of removal approach (coupling two-dimensional wave modelling with settling velocity data from 186 benthic sediment samples) to model shifts in both reef hydrodynamics and benthic sediment transport under different scenarios of mean reef submergence (MRS = +0 m, +0.5 m, +1 m) at two atoll rim reef sites in the Maldives. Under contemporary conditions (MRS = +0 m), we found that benthic sediment transport is likely occurring, consistent with active reef-to-island sediment connectivity. Under conditions of increased MRS, shifts in wave velocities, and in turn sediment potential mobility, were both non-linear and non-uniform. Significant between-site differences were found in the magnitude of projected shifts in sediment mobility under scenarios of increased MRS, which implies that morphological responses to increased MRS are likely to be diverse, even over local scales. Under increased MRS, the largest increases in sediment mobility were projected on the inner reef flat, whereas lagoonal zones remained as sinks for sediment deposition. We thus hypothesize that while reef islands will persist as sedimentary landforms under projected rates of MRS, lagoonward reef island migration is likely to occur. Findings have implications for predicting the future adaptive capacity of atoll nations. Our results highlight the need for national-scale vulnerability assessments to incorporate (1) potential increases in island mobility; (2) the importance of allowing natural sediment transport processes to occur (unhindered by human constructions); and (3) intra-regional diversity in reef system geomorphic responses to sea level rise.

中文翻译：

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模拟环礁岛系统海平面上升下的珊瑚礁流体动力学和沉积物流动性

摘要 未来海平面上升（SLR）将对低洼珊瑚礁岛屿产生重大影响。通常预计 SLR 会破坏礁岛的稳定，因为增加珊瑚礁淹没会导致更大的波浪，因此更大的能量传输穿过礁滩。然而，SLR 对礁滩沉积物运输和沉积物输送到岛屿海岸线的潜在影响知之甚少。在这里，我们使用去除流方法（将二维波浪模型与来自 186 个底栖沉积物样本的沉降速度数据耦合）来模拟在平均珊瑚礁淹没（MRS = +0 m）的不同情况下珊瑚礁流体动力学和底栖沉积物迁移的变化, +0.5 m, +1 m) 在马尔代夫的两个环礁边缘珊瑚礁地点。在当代条件下 (MRS = +0 m)，我们发现可能发生底栖沉积物迁移，这与活跃的珊瑚礁与岛屿沉积物连通性一致。在 MRS 增加的条件下，波速的变化以及沉积物潜在的流动性都是非线性和非均匀的。在 MRS 增加的情况下，沉积物流动性的预计变化幅度存在显着的站点间差异，这意味着对 MRS 增加的形态响应可能是多样的，即使在局部尺度上也是如此。在增加的 MRS 下，沉积物流动性的最大增加被预测在内礁滩，而泻湖区仍然是沉积物沉积的汇。因此，我们假设，虽然礁岛将在 MRS 预测速率下作为沉积地貌持续存在，但很可能会发生向泻湖礁岛的迁移。研究结果对预测环礁国家未来的适应能力有影响。我们的结果强调需要进行全国范围的脆弱性评估以纳入 (1) 岛屿流动性的潜在增加；(2) 允许自然沉积物运输过程发生（不受人类建筑阻碍）的重要性；(3) 珊瑚礁系统地貌响应对海平面上升的区域内多样性。