Collaborative Research: Investigating the Role of Coastal Polynya Variability in Modulating Antarctic Marine-Terminating Glacier Drawdown

南极冰盖是海平面上升的主要原因，其大部分质量损失发生在其边缘，那里是冰与海洋相遇的地方。冰川和冰流流向海岸，可以漂浮在水面上，形成冰架。冰架几乎占整个南极海岸线的一半，并阻止南极大陆内陆冰的流动;因此，它们对南极冰盖的整体稳定性不可或缺。冰架通过两个主要过程失去质量：冰山崩解和基底融化。两者的时间和空间波动是由各种过程驱动的;冰架融化的主要驱动力是邻近的南大洋提供的热量。反过来，海洋热量又受到冰架环境各个方面的驱动。海洋热含量变化的最重要因素之一是海冰的存在。这项研究将侧重于沿海冰间冰穴（海冰中的开放水域）的影响，它们如何调节当地的海洋环境，以及这种环境如何推动冰架基底融化。到目前为止，冰穴和冰架融化之间的关系还没有被描述在一个舌状的范围内。了解冰间湖的大小和持续时间、海洋分层和冰架融化之间的反馈以及这些反馈的强度，将提高描述对冰架长期稳定性的影响的能力，进而提高描述对整个南极冰盖的影响的能力。这项研究的一个重要方面是，它将为了解不同地理环境中冰架与海洋的相互作用提供一个框架。这一点，加上各种模型的改进，将有助于解释未来气候变化对这些系统的影响，因为它们的反应可能是相当可变的，总的来说，不同于冰盖的大规模反应。本研究主要围绕四个假设展开：（1）海岸冰穴的变化与冰架融化速率的变化存在相关性，这种相关性在南极各地存在差异; 2）冰缘层通过局部沃茨的分层作用，调节冰架融化和冰架增生之间的反馈关系; 3）冰缘带的范围与海底水深测量一起调节到达冰缘的温暖近海沃茨的体积; 4）冰穴与冰川冰之间的反馈作用强度因地理环境而异，并影响着长期的气候变化。冰川系统的长期稳定性。将结合海洋（麻省理工学院全球环流模型）和冰盖（冰盖和海平面系统模型）模型使用观测数据，包括探冰雷达、雷达和激光测高、现场水文数据以及从南大洋状态估计项目和南极BedMachine得出的数据集，以揭示潜在的动态。对观测数据的联合分析使得能够调查冰间湖、海洋和冰架信号及其在一系列环境中随时间的相互作用。该数据分析的结果还为建模任务提供了输入和验证数据，这将允许对我们观察中的反馈进行表征。耦合模拟将使我们能够研究冰间湖环流和冰架在不同的动力学制度之间的相互作用，并了解冰和海洋反馈随着时间的推移。诊断和解释冰棚-冰架相互作用的泛南极空间变异性是本研究的主要目标，并将本研究与针对特定区域相互作用过程的其他项目分开。因此，这项研究的重点是在南极海岸周围的七个初步目标网站，建立一个框架，解释耦合冰架海洋变异性在不同的地理环境范围内。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Most of the mass loss from the Antarctic Ice Sheet, a major contributor to sea level rise, occurs at its margins, where ice meets the ocean. Glaciers and ice streams flow towards the coast and can go afloat over the water, forming ice shelves. Ice shelves make up almost half of the entire Antarctic coastline, and hold back the flow of inland ice in Antarctica continent; thus they are integral to the overall stability of the Antarctic Ice Sheet. Ice shelves lose mass by two main processes: iceberg calving and basal melting. Temporal and spatial fluctuations in both are driven by various processes; a major driver of ice shelf melt is the heat provided by the neighboring Southern Ocean. Ocean heat, in turn, is driven by various aspects of the ice shelf environment. One of the most significant contributors to changes in the ocean’s heat content is the presence of sea ice. This research will focus on the effects of coastal polynyas (areas of open water amidst sea ice), how they modulate the local ocean environment, and how that environment drives ice shelf basal melting. To date, the relationship between polynyas and ice shelf melt has not been characterized on an Antarctic-wide scale. Understanding the feedbacks between polynya size and duration, ocean stratification, and ice shelf melt, and the strength of those feedbacks, will improve the ability to characterize influences on the long-term stability of ice shelves, and in turn, the Antarctic Ice Sheet as a whole. A critical aspect of this study is that it will provide a framework for understanding ice shelf-ocean interaction across a diverse range of geographic settings. This, together with improvements of various models, will help interpret the impacts of future climate change on these systems, as their responses are likely quite variable and, overall, different from the large-scale response of the ice sheet. This project will also provide a broader context to better design future observational studies of specific coastal polynya and ice shelf processes.This study focuses on four main hypotheses: 1) Variations of coastal polynya extent are correlated with those of the ice shelf melt rates, and this correlation varies around Antarctica; 2) Polynya extent modulates a feedback between ice shelf melt and accretion regimes through stratification of local waters; 3) Polynya extent together with seafloor bathymetry regulate the volume of warm offshore waters that reach ice margins; and 4) The strength of the feedback between polynya and glacier ice varies with geographic setting and influences the long-term stability of the glacial system. Observational data, including ice-penetrating radar, radar and laser altimetry, and in situ hydrographic data, and derived data sets from the Southern Ocean State Estimate (SOSE) project and BedMachine Antarctica, will be used in conjunction with ocean (MIT global circulation model, MITgcm) and ice sheet (Ice sheet and Sea-level System Model, ISSM) models to reveal underlying dynamics. The joint analysis of the observational data enables an investigation of polynya, ocean, and ice shelf signals and their interplay over time across a range of settings. The results of this data analysis also provide inputs and validation data for the modeling tasks, which will allow for characterization of the feedbacks in our observations. The coupled modeling will enable us to examine the interaction between polynya circulation and ice shelves in different dynamical regimes and to understand ice and ocean feedback over time. Diagnosing and interpreting the pan-Antarctic spatial variability of the polynya-ice shelf interaction are the main objectives of this research and separates this study from other projects targeted at the interactive processes in specific regions. As such, this research focuses on seven preliminary target sites around the Antarctic coast to establish a framework for interpreting coupled ice shelf-ocean variability across a diverse range of geographic settings.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.