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

合作研究：调查沿海冰间湖变化在调节南极海洋终止冰川水位下降中的作用

• 批准号: 2205008
• 负责人: Catherine Walker
• 金额: $ 66.34万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2025-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2205008&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Role; Coastal

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.

南极冰盖是海平面上升的主要原因之一，其大部分质量损失发生在冰盖的边缘，即冰与海洋的交汇处。冰川和冰流流向海岸，漂浮在水面上，形成冰架。冰架几乎构成了整个南极海岸线的一半，并阻碍了南极大陆内陆冰的流动；因此，它们是南极冰盖整体稳定的组成部分。冰架的质量损失主要有两个过程：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；邻近的南大洋提供的热量是冰架融化的主要驱动力。反过来，海洋热量是由冰架环境的各个方面驱动的。海洋热含量变化的最重要因素之一是海冰的存在。这项研究将集中在沿海冰湖（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。迄今为止，融冰和冰架融化之间的关系还没有在整个南极洲范围内得到表征。了解多冰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。这项研究的一个关键方面是，它将为理解不同地理环境下的冰架-海洋相互作用提供一个框架。这一点，再加上各种模式的改进，将有助于解释未来气候变化对这些系统的影响，因为它们的反应很可能变化很大，总的来说，与冰盖的大规模反应不同。该项目还将提供一个更广泛的背景，以便更好地设计未来对特定海岸冰湖和冰架过程的观测研究。本研究主要提出了四个假设：1)沿海多冰区范围的变化与冰架融化速率的变化具有相关性，这种相关性在南极洲周围存在差异；(2)多冰区范围通过局部水域的分层调节冰架融化和增生机制之间的反馈；(3)冰谷范围和海底水深测量共同调节了到达冰缘的温暖近海水域的体积；(4)冰川与冰间的反馈强度随地理环境的变化而变化，影响冰川系统的长期稳定性。观测数据，包括破冰雷达、雷达和激光测高、现场水文数据，以及来自南大洋状态估计（SOSE）项目和南极床机的衍生数据集，将与海洋（麻省理工学院全球环流模型，MITgcm）和冰盖（冰盖和海平面系统模型，ISSM）模型一起使用，以揭示潜在的动力学。通过对观测数据的联合分析，可以对冰湖、海洋和冰架信号及其在一系列环境下随时间的相互作用进行调查。该数据分析的结果还为建模任务提供了输入和验证数据，这将允许在我们的观察中对反馈进行表征。耦合模型将使我们能够在不同的动力机制下检查冰湖环流和冰架之间的相互作用，并了解冰和海洋随时间的反馈。诊断和解释多冰湖-冰架相互作用的泛南极空间变异性是本研究的主要目标，并将本研究与其他针对特定区域相互作用过程的项目区分开来。因此，本研究将重点放在南极海岸周围的七个初步目标地点，以建立一个框架，用于解释不同地理环境下的冰架-海洋耦合变异性。该奖项反映了美国国家科学基金会的法定使命，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。

项目成果

Stratification Breakdown in Antarctic Coastal Polynyas. Part I: Influence of Physical Factors on the Destratification Time Scale

南极沿海冰间湖的层结分解。

• DOI: 10.1175/jpo-d-22-0218.1
• 发表时间: 2023
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Xu, Yilang;Zhang, Weifeng;Maksym, Ted;Ji, Rubao;Li, Yun
• 通讯作者: Li, Yun

Stratification Breakdown in Antarctic Coastal Polynyas. Part II: Influence of an Ice Tongue and Coastline Geometry

南极沿海冰间湖的层结分解。

• DOI: 10.1175/jpo-d-22-0219.1
• 发表时间: 2023
• 期刊: Journal of Physical Oceanography
• 影响因子: 3.5
• 作者: Xu, Yilang;Zhang, Weifeng;Maksym, Ted;Ji, Rubao;Li, Yun
• 通讯作者: Li, Yun