Deep uncertainty describes situations when there is either ignorance or disagreement over (1) models used to describe key system processes and (2) probability distributions used to characterize the uncertainty of key variables and parameters. Future projections of Antarctic ice sheet (AIS) mass loss remain characterized by deep uncertainty. This complicates decisions on long‐lived coastal protection projects when determining what margin of safety to implement. If the chosen margin of safety does not properly account for uncertainties in sea level rise, the effectiveness of flood protection could decrease over time, potentially putting lives and properties at a greater risk. To address this issue, we develop a flood damage allowance framework for calculating the height of a flood protection strategy needed to ensure that a given level of financial risk is maintained. The damage allowance framework considers decision maker preferences such as planning horizons, protection strategies, and subjective views of AIS stability. We use Manhattan—with the population and built environment fixed in time—to illustrate how our framework could be used to calculate a range of damage allowances based on multiple plausible scenarios of AIS melt. Under high greenhouse gas emissions, we find that results are sensitive to the selection of the upper limit of AIS contributions to sea level rise. Design metrics that specify financial risk targets, such as expected flood damage, allow for the calculation of avoided flood damages (i.e., benefits) that can be combined with estimates of construction cost and then integrated into existing financial decision‐making approaches (e.g., benefit‐cost analysis).

中文翻译：

---

在海平面上升中具有高度不确定性的海岸保护洪水赔偿限额框架。

深度不确定性描述的情况是，对于（1）用于描述关键系统过程的模型和（2）用于表征关键变量和参数的不确定性的概率分布，存在无知或意见分歧。对南极冰盖（AIS）质量损失的未来预测仍然具有很大的不确定性。在确定实施何种安全裕度时，这会使长期的沿海保护项目的决策变得复杂。如果所选的安全范围不能适当考虑海平面上升的不确定性，那么防洪作用的有效性可能会随着时间的流逝而降低，从而可能使生命和财产面临更大的风险。为了解决这个问题，我们开发了洪水损失补贴框架，用于计算防洪策略的高度，以确保维持给定水平的财务风险。损害赔偿框架考虑了决策者的偏好，例如计划范围，保护策略以及AIS稳定性的主观观点。我们使用曼哈顿（人口和建筑环境在时间上固定）来说明如何使用我们的框架基于AIS融化的多种可能情况来计算一系列损害赔偿。在高温室气体排放下，我们发现结果对选择AIS对海平面上升贡献的上限很敏感。指定财务风险目标（例如预期的洪水破坏）的设计指标可以计算避免的洪水破坏（例如，