Present and Future Stability of Larsen C Ice Shelf (SOLIS)

1995年和2002年，南极半岛Larsen A和B冰架的迅速崩解被广泛报道，这是气候变化对该地区可能产生的巨大影响的非同寻常的证明。冰架的破裂特别引起科学界和公众的关注，主要有两个原因：[a]冰架主要是由冰川和冰流（将冰从冰架内部运送到冰架边缘的受限、快速流动的“传送带”）流入的冰维持的。由于冰架崩塌导致支撑力消失，这些冰川和冰流会加速，从而增加从冰架内部向海洋的排放。这可能会导致这些冰盖迅速而持续地萎缩，海平面也会急剧上升。[b]除了由于[a]而加速冷融水的输入外，冰架解体还可能导致海洋环流区域格局的改变和南极底水的形成。AABW是全球海洋环流的重要贡献者，而全球海洋环流反过来又调节全球气候。如果AABW形成的改变可以引发这种环流的变化，那么冰架崩塌可能间接导致全球气候模式的改变。如果南极半岛的气候变暖速度继续保持在异常高的水平（目前为每世纪4摄氏度），那么该地区剩余冰架的稳定性就会受到质疑。拉森C是南极半岛上最大的冰架，也是2002年崩塌的拉森B的南部邻居，在过去的15年中逐渐变薄。这可能表明拉森C冰架已经进入了退缩或可能崩溃的过程。如果冰架崩解（即使是部分），在这次事件中失去的冰架冰很可能比之前在南极半岛发生的所有事件加起来都要多。因此，关键问题是：拉森C冰架将来有可能崩溃吗？拟议的项目旨在回答这个问题。冰架的稳定性受到一系列冰内部控制因素的控制，包括[a]冰的成分和结构；[b]应力强度（作为一种不稳定力）和冰断裂韧性（冰抵抗应力的能力，从而作为一种稳定力）之间的平衡；[c]裂陷的模式和过程。气候变化不仅可以直接也可以通过一系列外部控制（质量平衡从而导致冰架总厚度；冰架几何形状；海洋学和海冰过程；气象学）间接地迫使内部控制。在描述气候条件下的内部控制和直接和间接（通过外部控制）强迫建模时，我们建议采用三层策略：[a]使用标准地球物理方法进行实地调查，作为项目的核心活动，提供所需的地面控制；[b]利用现有的遥感技术将实地数据提高到整个冰架；[c]使用升级数据的适应计算机模型（以前成功应用于Filchner-Ronne和Larsen B冰架）的强迫。模型输出将允许[a]确定拉森C冰架目前的稳定程度；[b]一系列未来情景的模拟，包括冰架迅速退缩或解体；[c]确定最现实的未来情景。这将使我们能够断定拉森C冰架将来是否有可能崩溃。

The widely publicised rapid disintegrations of the Larsen A and B ice shelves on the Antarctic Peninsula in 1995 and 2002 were extraordinary demonstrations of the dramatic impact that climatic changes can have on this region. Ice shelf break-up is of particular scientific and public concern for two main reasons: [a] Ice shelves are sustained principally by inflow of ice from glaciers and ice streams (confined, fast-flowing 'conveyor belts' that transport ice from the interior of ice sheets to their margins). As the buttressing force is removed as a result of ice shelf collapse, these glaciers and ice streams can speed up and thus increase discharge from the ice sheet interior to the ocean. This could potentially lead to rapid and sustained shrinkage of these ice sheets and an equally dramatic increase in sea level. [b] In addition to accelerated input of cold melt water as a result of [a], ice shelf disintegration may also lead to modification of regional patterns of ocean circulation and the formation of Antarctic Bottom Water (AABW). AABW is an important contributor to the global ocean circulation which in turn regulates world-wide climate. If modification of AABW formation can trigger changes in this circulation, ice shelf collapse could indirectly contribute to alterations of world-wide climate patterns. If rates of climatic warming on the Antarctic Peninsula continue to be anomalously high (presently ~ 4 degrees C per century), the stability of the remaining ice shelves in this region comes into question. Larsen C, as the largest ice shelf on the Antarctic Peninsula and the southern neighbour of Larsen B which collapsed in 2002, has thinned progressively over the past 15 years. This could indicate that the Larsen C ice shelf has already entered a process of retreat or possibly collapse. If the ice shelf were to disintegrate (even partially), it is likely that more shelf ice would be lost in this single incident than has been lost by all previous incidents on the Antarctic Peninsula taken together. The key question is therefore: Is the Larsen C ice shelf likely to collapse in the future? The proposed project aims to answer that question. The stability of an ice shelf is controlled by a range of ice-internal controls, including [a] ice composition and structure; [b] the balance between stress intensity (acting as a de-stabilising force) and ice fracture toughness (the ability of ice to resist stress, thus acting as a stabilising force); and [c] patterns and processes of rifting. Climatic changes can force the internal controls not only directly but also indirectly via a range of external controls (mass balance and thus total ice shelf thickness; ice shelf geometry; oceanographic and sea ice processes; meteorology). In characterising the internal controls and modelling direct and indirect (via the external controls) forcing by climatic conditions, we propose to adopt a three-tier strategy: [a] field-based investigations using standard geophysical methods as the core activity of the project providing the required ground control; [b] upscaling of the field data to the whole ice shelf using established remote sensing techniques; and [c] forcing of an adapted computer model (previously applied successfully to the Filchner-Ronne and Larsen B ice shelves) using the upscaled data. The model outputs will allow [a] identification of how stable the Larsen C ice shelf is at present; [b] simulation of a range of future scenarios including rapid ice shelf retreat or disintegration; and [c] identification of the most realistic future scenario. This will enable us to conclude whether the Larsen C ice shelf is likely to collapse in the future.