Investigating the exchange flow in glacial fjords through an estuarine lens

通过河口透镜研究冰川峡湾的交换流

• 批准号: 2023415
• 负责人: Rebecca Jackson
• 金额: $ 61.75万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023415&HistoricalAwards=false
• 关键词: Investigating; exchange; flow; glacial; fjords

With the Greenland Ice Sheet losing mass at an accelerating rate, a poor understanding of ocean-glacier interactions contributes to the uncertainties in sea level rise projections. Although fjords cannot be resolved in global climate models, fjord processes must be understood – and eventually parameterized – in order to study the global impacts of both ocean warming on glacier retreat and increased glacial freshwater on ocean circulation. Fjords connect Greenland’s marine-terminating glaciers to the continental shelf ocean, forming long, narrow conduits for the export of glacial freshwater and the import of oceanic heat to melt ice. As such, fjord dynamics modulate the exchange of heat and freshwater between the ocean and glaciers, and processes of climatic relevance are affected by both directions of this ocean-ice interaction. In terms of the cryosphere’s impact on the ocean, the Greenland Ice Sheet is losing mass at an accelerating pace, and ocean warming has been implicated as a trigger for recent glacier changes via submarine melting in fjords. In the other direction, increased freshwater from Greenland can impact ocean dynamics and ecosystems – locally within fjords, regionally in coastal currents, and potentially globally by altering the deep-convection in basins of the North Atlantic. Despite the importance of fjord circulation to ocean-glacier interactions, we have a limited understanding of the fjord processes that transport heat, salt and freshwater between the shelf ocean and glaciers. Recent observations have demonstrated the importance of two primary modes of circulation: freshwater buoyancy forcing from subglacial discharge at the glacier, and synoptic external forcing from winds and coastal trapped waves on the shelf. Drawing on these observations, the investigators will carry out numerical simulations of a fjord and its adjacent shelf, for both a quasi-realistic fjord and an idealized set of simulations. The goal of the project is to investigate the dynamics of the buoyancy-driven flow at the fjord-scale, and how this circulation interacts with synoptic external forcing to drive a net transport of heat, salt and freshwater. The relative contributions of these modes of circulation to mixing and the total exchange flow will be assessed spatially within fjords with characteristics representative of Greenland’s major fjords. This project will support K-12 education outreach, in close collaboration with two educational specialists at Rutgers. The PIs will help develop polar data kits with fjord observations and idealized model output for students to use in the Rutgers’ Data Jam Program, an opportunity for students to get hands-on experience working with data and developing scientific skills. The project will involve participation in Data Jam activities and also the 4-H STEM Ambassador program at Rutgers, where the PIs will engage with 9th graders from underserved schools and develop an educational component focused on melting of glaciers, sea level rise, and climate change. Additionally, this project, which brings together scientists across a wide range of career stages, will train a PhD student and support an early career researcher.New observations from near-glacier surveys and downstream moorings in fjords have been instrumental for understanding fjord exchange flow. Dynamical frameworks have recently been developed for external (shelf and wind) forcing in isolation, but no theory exists to describe the buoyancy-driven flow that transports tracers through the fjord or the impact of external forcing on this exchange. A realistic fjord model could untangle these intertwined dynamics and provide new insights into processes driving ocean-cryosphere exchange. While glacial fjords are fundamentally estuaries – coastal embayments where terrestrial freshwater mixes into seawater – they do not fit easily into traditional estuarine paradigms. However, there are many useful frameworks to build on from the coastal and estuarine world. This project will investigate fjord dynamics through an estuarine lens, drawing on better-studied processes in standard estuaries, and will attempt to expand estuarine paradigms to include glacial fjords. These questions will be addressed by a team of investigators with complementary expertise in fjord dynamics and ocean-ice interactions, estuarine dynamics, and coastal modeling and shelf processes.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.

随着格陵兰冰盖加速流失，对海洋-冰川相互作用的了解不足导致海平面上升预测的不确定性，尽管全球气候模型无法解决峡湾问题，但必须了解峡湾过程并最终将其参数化。为了研究海洋变暖对冰川退缩和冰川淡水增加对海洋环流的全球影响，峡湾将格陵兰岛的海洋终止冰川与大陆架海洋连接起来，形成了海洋。用于输出冰川淡水和输入海洋热量以融化冰的狭长通道因此，峡湾动态调节海洋和冰川之间的热量和淡水交换，而与气候相关的过程受到这两个方向的影响。就冰冻圈对海洋的影响而言，格陵兰冰盖正在加速失去质量，海洋变暖被认为是最近海底冰川变化的触发因素。另一方面，来自格陵兰岛的淡水增加会影响海洋动态和生态系统——局部的峡湾、区域性的沿海流，以及可能通过改变北大西洋盆地的深层对流而影响全球。从环流到海洋-冰川相互作用，我们对在陆架海洋和冰川之间输送热量、盐和淡水的峡湾过程了解有限。最近的观察证明了两种主要模式的重要性。循环：来自冰川冰下排放的淡水浮力，以及来自陆架上的风和沿海困波的天气外力，研究人员将对峡湾及其邻近陆架进行数值模拟。 - 现实的峡湾和一组理想化的模拟该项目的目标是研究峡湾规模的浮力驱动流的动力学，以及这种环流如何与天气外部相互作用。迫使驱动热、盐和淡水的净运输。将在具有格陵兰岛主要峡湾特征的峡湾内对这些循环模式的相对贡献和总交换流进行评估。该项目将支持 K-12 教育。 PI 将与罗格斯大学的两位教育专家密切合作，帮助开发带有峡湾观测和理想化模型输出的极地数据包，供学生在罗格斯大学的 Data Jam 项目中使用，这是学生获得知识的机会。该项目将涉及参与 Data Jam 活动以及罗格斯大学的 4-H STEM 大使计划，其中 PI 将与服务不足的学校的 9 年级学生互动，并开发一个以教育为重点的内容。此外，该项目汇集了各个职业阶段的科学家，将培训一名博士生并支持一名早期职业研究员。来自近冰川调查和研究的新观察结果。下游峡湾中的系泊装置有助于理解峡湾交换流，最近开发了针对孤立的外部（陆架和风）强迫的动力框架，但不存在描述通过峡湾输送示踪剂的浮力驱动流或影响的理论。一个现实的峡湾模型可以解开这些相互交织的动力学，并为驱动海洋-冰冻圈交换的过程提供新的见解，而冰川峡湾从根本上来说是驱动过程。河口——陆地淡水与海水混合的沿海海湾——它们并不容易融入传统的河口范式。然而，该项目将通过河口视角研究峡湾动态。对标准河口的过程​​进行更好的研究，并将尝试扩大河口范式以包括冰川峡湾。这些问题将由一个团队解决。由在峡湾动力学和海冰相互作用、河口动力学以及沿海建模和陆架过程方面具有互补专业知识的研究人员组成。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标准进行评估，被认为值得支持。