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来影响气候，在目前的气候下，冰盖质量损失的大约一半归因于冰山的崩解。冰山漂流和融化时沉积的淡水会影响海洋循环、海冰形成和生物初级生产力。此外，冰山从冰架上崩解，这是冰盖的浮动延伸，通过减少冰架对上游地面冰向海流动提供的阻力，可以影响冰盖的演化和海平面上升。从冰架上崩解出来的大部分物质以板状冰山的形式出现，这些冰山通常有数百米厚，长度和宽度都在几十到数百公里左右。当被称为裂缝的全厚度冰架断裂扩展到冰架边缘时，就会发生板状崩解。这种冰解事件很少见，通常在单个冰架上发生数十年的冰川崩解事件。列表冰解行为的变化，即冰解事件的大小和频率，可以强烈地影响气候和冰盖的演变。然而，在气候模型中，表格崩解行为及其对气候变化的响应既不能被很好地理解，也不能被准确地表示。在这个项目中，将开发气候模型的表格崩解参数化。该参数将根据一系列现实的和理想化的世纪尺度的表格崩解模拟产生的数据得出，该模拟将使用一个可应用于单个冰盖-冰架系统的新的冰流和破坏框架：CD-MPM-SSA(Shelfy-Stream近似的连续损伤物质点方法)。在这些模拟过程中，冰架的几何形状、冰的机械/流变性以及海洋温度等气候强迫因素将发生变化，以确定裂谷和崩解的反应。从这些实验中得出的冰解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，在那里它将与粘结粒子冰山模型相耦合。然后，将进行实验，研究冰山崩解行为的变化与气候之间的反馈。这个项目的成功将提高我们对冰块预算、冰盖演化和海洋淡水通量的理解和表达，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智力优势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.