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: 2205009
• 负责人: Helene Seroussi
• 金额: $ 17.54万
• 依托单位: Dartmouth College
• 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=2205009&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.

南极冰盖的大部分质量损失是海平面上升的主要原因，发生在其边缘，冰川和冰流流向海岸，并漂浮在水面上，形成冰架。冰架几乎占据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，因此它们对于南极冰盖的整体稳定性至关重要，主要有两个原因。过程：冰山崩解和基底融化都是由各种过程驱动的；冰架融化的主要驱动因素是邻近的南大洋热量提供的热量，而冰架融化的主要驱动因素是由邻近的南大洋热量提供的。冰架环境。海洋热含量变化的最重要因素之一是海冰的存在。这项研究将重点关注沿海冰间湖（海冰中的开放水域）的影响，以及它们如何调节当地海洋。环境，以及如何迄今为止，冰间湖与冰架融化之间的关系尚未在南极范围内得到表征。了解冰间湖的大小和持续时间、海洋分层和冰架融化以及强度之间的反馈。这些反馈的结果将提高描述冰架长期稳定性影响的能力，进而提高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，它将为理解冰提供一个框架。这与各种模型的改进一起，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相当多变，而且总体而言与大型系统不同。该项目还将提供更广泛的背景，以更好地设计未来对特定沿海冰间湖和冰架过程的观测研究。本研究重点关注四个主要假设：1）沿海冰间湖范围的变化与冰间湖范围的变化相关。冰架融化速率，并且这种相关性变化南极洲周围；2）冰间湖范围通过当地水域的分层调节冰架融化和增生状态之间的反馈；3）冰间湖范围与海底测深一起调节到达冰边缘的近海温暖水域的体积；冰间湖和冰川冰之间的反馈随地理环境的不同而变化，并影响冰川系统的长期稳定性，包括透冰雷达、雷达和激光。高度测量、现场水文数据以及来自南大洋状态估计 (SOSE) 项目和 BedMachine Antarctica 的派生数据集将与海洋（MIT 全球环流模型，MITgcm）和冰盖（冰盖和海洋）结合使用。水平系统模型（ISSM）模型来揭示观测数据的联合分析，可以研究冰间湖、海洋和冰架信号及其在一系列设置中随时间的相互作用。还为建模任务提供输入和验证数据，这将使我们能够对观测中的反馈进行表征，耦合建模将使我们能够检查不同动态状态下冰间湖环流和冰架之间的相互作用，并了解冰和海洋的反馈。随着时间的推移，诊断和解释冰间湖-冰架相互作用的泛南极空间变化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区分开来。初步的南极海岸周围的目标地点建立一个框架，用于解释不同地理环境中冰架-海洋的耦合变化。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查进行评估，被认为值得支持标准。