OPP-PRF Calving, Icebergs, and Climate

冰山通过控制来自冰盖的淡水如何分配到海洋中来影响气候，在当前气候下，大约一半的冰盖质量损失归因于冰山崩解。冰山漂流和融化时沉积的淡水会影响海洋环流、海冰形成和生物初级生产力。此外，冰山从冰架（冰盖的浮动延伸部分）崩解，可以通过减少冰架对上游接地冰向海流动提供的阻力应力来影响冰盖演变和海平面上升。大部分从冰架上崩解下来的物质都是以平板状冰山的形式出现的，这些冰山通常有几百米厚，长度和宽度都在几十到几百公里的数量级上。当被称为裂缝的全层冰架裂缝扩展到冰架边缘时，就会发生平板状裂解。这些裂冰事件并不频繁，通常在单个冰架上的事件之间有几十年的时间。产犊行为的变化，即，冰解事件的规模和频率可以强烈影响气候和冰盖的演变。然而，表格式产犊行为，以及它如何响应气候变化，既没有很好地理解，也没有准确地表示在气候模式中。参数化将根据从一系列现实和理想化的世纪规模的表格产犊模拟，这将是一个新的冰流和损害框架，可以应用于规模的个别冰盖冰架系统：CD-MPM-SSA（连续损伤材料点方法的Shelfy-Stream近似）。在这些模拟过程中，冰架的几何形状，冰的机械/流变特性，以及海洋温度等气候强迫将发生变化，以确定断裂和产犊反应。从这些实验中得出的产犊参数化将在地球物理流体动力学实验室（GFDL）的气候模型中实施，在那里它将与粘结颗粒冰山模型相结合。然后，将进行实验以研究冰山崩解行为和气候变化之间的反馈。该项目的成功将提高我们对冰量收支、冰盖演变和海洋淡水通量的理解和代表性，并将改善对气候变化和海平面上升的预测。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Icebergs influence climate by controlling how freshwater from ice sheets is distributed into the ocean, where roughly half of ice sheet mass loss is attributed to iceberg calving in the current climate. The freshwater deposited by icebergs as they drift and melt can affect ocean circulation, sea-ice formation, and biological primary productivity. Furthermore, calving of icebergs from ice shelves, the floating extensions of ice sheets, can influence ice sheet evolution and sea-level rise by reducing the resistive stresses provided by ice shelves on the seaward flow of upstream grounded ice. The majority of mass calved from ice shelves occurs in the form of tabular icebergs, which are typically hundreds of meters thick and on the order of tens to hundreds of kilometers in length and width. Tabular calving occurs when full-thickness ice shelf fractures known as rifts propagate to the edges of the ice shelf. These calving events are infrequent, often with decades between events on an individual ice shelf. Changes in tabular calving behavior, i.e., the size and frequency of calving events, can strongly influence climate and ice sheet evolution. However, tabular calving behavior, and how it responds to changes in climate, is neither well understood nor accurately represented in climate models.In this project, a tabular calving parameterization for climate models will be developed. The parameterization will be derived according to data generated from a series of realistic and idealized century-scale tabular calving simulations, which will be performed with a novel ice flow and damage framework that can be applied at the scale of individual ice sheet-ice shelf systems: the CD-MPM-SSA (Continuum Damage Material Point Method for Shelfy-Stream Approximation). During these simulations, the geometry of the ice shelf, mechanical/rheological properties of the ice, and climate forcings such as ocean temperature will be varied to determine the rifting and calving response. The calving parameterization derived from these experiments will be implemented in a Geophysical Fluid Dynamics Laboratory (GFDL) climate model, where it will be coupled with a bonded-particle iceberg model. Then, experiments will be run to study the feedback between changes in iceberg calving behavior and climate. Success of this project will improve our understanding and representation of the ice mass budget, ice sheet evolution, and ocean freshwater fluxes, and will improve projections of climate change and sea-level rise.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.