Uncertainty about sea-level rise is dominated by uncertainty about iceberg calving, mass loss from glaciers or ice sheets by fracturing. Review of the rapidly growing calving literature leads to a few overarching hypotheses. Almost all calving occurs near or just downglacier of a location where ice flows into an environment more favorable for calving, so the calving rate is controlled primarily by flow to the ice margin rather than by fracturing. Calving can be classified into five regimes, which tend to be persistent, predictable, and insensitive to small perturbations in flow velocity, ice characteristics, or environmental forcing; these regimes can be studied instrumentally. Sufficiently large perturbations may cause sometimes-rapid transitions between regimes or between calving and noncalving behavior, during which fracturing may control the rate of calving. Regime transitions underlie the largest uncertainties in sea-level rise projections, but with few, important exceptions, have not been observed instrumentally. This is especially true of the most important regime transitions for sea-level rise. Process-based models informed by studies of ongoing calving, and assimilation of deep-time paleoclimatic data, may help reduce uncertainties about regime transitions. Failure to include calving accurately in predictive models could lead to large underestimates of warming-induced sea-level rise. ▪ Iceberg calving, the breakage of ice from glaciers and ice sheets, affects sea level and many other environmental issues. ▪ Modern rates of iceberg calving usually are controlled by the rate of ice flow past restraining points, not by the brittle calving processes. ▪ Calving can be classified into five regimes, which are persistent, predictable, and insensitive to small perturbations. ▪ Transitions between calving regimes are especially important, and with warming might cause faster sea-level rise than generally projected.

中文翻译：

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冰山崩解：制度和转变


海平面上升的不确定性主要是冰山崩解、冰川或冰盖破裂造成的质量损失的不确定性。对快速增长的产犊文献的回顾得出了一些总体假设。几乎所有的崩解都发生在冰川附近或冰川下方，冰流入更有利于崩解的环境，因此崩解率主要由流向冰缘的流量控制，而不是通过破裂来控制。崩解可分为五种模式，这些模式往往是持久的、可预测的，并且对流速、冰特性或环境强迫的小扰动不敏感；这些制度可以通过仪器进行研究。足够大的扰动有时可能会导致状态之间或产犊和非产犊行为之间的快速转变，在此期间，压裂可能会控制产犊速率。制度转变是海平面上升预测中最大的不确定性的根源，但除了少数重要的例外，尚未通过仪器观察到。对于海平面上升最重要的政权转变尤其如此。基于过程的模型，通过对正在进行的产犊研究和深时古气候数据的同化，可能有助于减少政权过渡的不确定性。如果未能准确地将产犊纳入预测模型，可能会导致对变暖引起的海平面上升的大幅低估。 ▪ 冰山崩解，即冰川和冰盖的冰破裂，会影响海平面和许多其他环境问题。 ▪ 现代冰山崩解速率通常由冰流过限制点的速率控制，而不是由脆性崩解过程控制。 ▪ 产犊可分为五种模式，这些模式是持久的、可预测的且对小扰动不敏感。 ▪ 产犊期之间的转变尤其重要，并且随着变暖可能会导致海平面上升速度比一般预测更快。