Future sea-level rise poses an existential threat for many river deltas, yet quantifying the effect of sea-level changes on these coastal landforms remains a challenge. Sea-level changes have been slow compared to other coastal processes during the instrumental record, such that our knowledge comes primarily from models, experiments, and the geologic record. Here we review the current state of science on river delta response to sea-level change, including models and observations from the Holocene until 2300 CE. We report on improvements in the detection and modeling of past and future regional sea-level change, including a better understanding of the underlying processes and sources of uncertainty. We also see significant improvements in morphodynamic delta models. Still, substantial uncertainties remain, notably on present and future subsidence rates in and near deltas. Observations of delta submergence and land loss due to modern sea-level rise also remain elusive, posing major challenges to model validation. ▪ There are large differences in the initiation time and subsequent delta progradation during the Holocene, likely from different sea-level and sediment supply histories. ▪ Modern deltas are larger and will face faster sea-level rise than during their Holocene growth, making them susceptible to forced transgression. ▪ Regional sea-level projections have been much improved in the past decade and now also isolate dominant sources of uncertainty, such as the Antarctic ice sheet. ▪ Vertical land motion in deltas can be the dominant source of relative sea-level change and the dominant source of uncertainty; limited observations complicate projections. ▪ River deltas globally might lose 5% (∼35,000 km2) of their surface area by 2100 and 50% by 2300 due to relative sea-level rise under a high-emission scenario.

中文翻译：

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河流三角洲和海平面上升


未来海平面上升对许多河流三角洲构成生存威胁，但量化海平面变化对这些沿海地貌的影响仍然是一个挑战。在仪器记录期间，与其他沿海过程相比，海平面变化缓慢，因此我们的知识主要来自模型、实验和地质记录。在这里，我们回顾了河流三角洲对海平面变化响应的科学现状，包括从全新世到公元 2300 年的模型和观测。我们报告了过去和未来区域海平面变化的检测和建模方面的改进，包括更好地了解潜在过程和不确定性来源。我们还看到形态动力学三角洲模型的显着改进。尽管如此，仍然存在很大的不确定性，特别是三角洲及其附近当前和未来的沉降率。对现代海平面上升导致的三角洲淹没和土地损失的观测也仍然难以捉摸，这给模型验证带来了重大挑战。 ▪ 全新世时期三角洲的起始时间和随后的进积存在很大差异，这可能是由于不同的海平面和沉积物供应历史所致。 ▪ 现代三角洲面积更大，并且将面临比全新世生长期间更快的海平面上升，使它们容易受到强迫海侵。 ▪ 区域海平面预测在过去十年中已得到很大改善，现在还隔离了主要的不确定性来源，例如南极冰盖。 ▪ 三角洲的垂直陆地运动可能是相对海平面变化的主要来源和不确定性的主要来源；有限的观察使预测变得复杂。 ▪ 由于高排放情景下海平面相对上升，全球河流三角洲的表面积到 2100 年可能会减少 5%（约 35,000 平方公里），到 2300 年可能会减少 50%。