Collaborative Research: Submarine Melting of Greenland's Glaciers: What are the relevant ocean dynamics?

合作研究：格陵兰岛冰川海底融化：相关的海洋动力学是什么？

• 批准号: 1550290
• 负责人: Patrick Heimbach
• 金额: $ 2.75万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-05-01 至 2015-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1550290&HistoricalAwards=false
• 关键词: Collaborative; Research; Submarine; Melting; Greenland

Intellectual Merit: Submarine melting of Greenland's glaciers has emerged as a key term in the ice sheet?s mass balance and as a plausible trigger for their recent acceleration, which contributed to doubling Greenland's contribution to sea-level rise. Notwithstanding its importance, our understanding of submarine melting is limited and it is presently absent or crudely parameterized in glacier, ice sheet and climate models. Greenland's tidewater glaciers end in about 600 to 800 m deep, long fjords that connect the margins of the ice sheet to the shelf. The glaciers termini are typically grounded several hundreds of meters below sea-level and, as such, are exposed to a thick portion of the fjord's water column. Unique data, recently collected by two of the investigators, from two large glacial fjords in south-east Greenland show that these are filled year-round with cold, fresh waters of Arctic origin and warm, salty waters of subtropical origin whose different properties influence the circulation at the ice-edge. Furthermore, ship-based and moored velocity measurements show that the fjords are characterized by fast, highly variable, sheared flows and a vigorous fjord/shelf exchange which, likely, play a role in transporting heat to the glaciers termini. The implication is that submarine melt rates depend on a suite of oceanic processes including externally forced fjord circulations, fjord/shelf exchange and the distribution of properties on the shelf. Yet, the details of how these processes may contribute to the submarine melt rate or affect its variability are presently unknown.This project will fill this gap by combining the analysis of ship-based and moored data from the two fjords with a hierarchy of models (laboratory and numerical) to identify the parameters and mechanisms which control the properties and circulation in the fjords and the rate of submarine melting at the ocean/glacier interface. Having identified the controls on the submarine melt rate, the project investigators will then use historical oceanographic and atmospheric data to determine fjord conditions and submarine melt rates for the period preceding the acceleration of the glaciers when no fjord data are available. Climate model predictions will be used to estimate the potential impact of future oceanic variability on submarine melting of Greenland?s glaciers. Collaborations with experts in outlet glacier dynamics, the physics of the ice-ocean boundary and fjord circulations will provide expertise in related disciplines and a two-way exchange of information for this intrinsically multidisciplinary problem. The work proposed is aimed at understanding a newly discovered wiring of the climate system: that ocean variability can have a rapid and direct impact on the Greenland's ice sheet mass balance. It is timely because of the large and unpredicted changes that are occurring in Greenland and relevant because ice sheet/ocean interactions are presently absent from climate and ice sheet/glacier models. It is complementary to the study of ice sheet/ocean interactions around Antarctica (the more studied of the two) since both the large-scale ocean circulation and the presence of narrow, long fjords in Greenland contribute a unique set of relevant dynamical mechanisms.Broader Impacts: This work seeks to increase our understanding of a previously overlooked, important connection in our climate system which has profound implications for our ability to accurately predict sea-level rise - an issue of grave and immediate societal concern. It is expected that results from this work will contribute to the inclusion of the relevant dynamics (even if in parameterized form) in future models and, as such, lead to the improvement of future sea level predictions. The work plan involves several international experts from complementary fields and, as such, will contribute to fostering interactions between the multiple disciplines involved and beyond national boundaries. It involves two graduate students and one post-doc who will be exposed to a cutting-edge problem and multidisciplinary team of researchers. Results from this project will be widely disseminated to scientists across disciplines, as demonstrated by the PIs long-track of organizing summer schools and working groups, and to the public through different media outlets, as shown by the recent coverage of the investigators' Greenland work in venues that include the Museum of Science in Boston, the New York Times, the Weather Channel and Italian National Television.

智力价值：格陵兰岛冰川的海底融化已成为冰盖质量平衡的一个关键术语，并且可能是其最近加速的触发因素，这使得格陵兰岛对海平面上升的贡献增加了一倍。尽管它很重要，但我们对海底融化的了解是有限的，目前在冰川、冰盖和气候模型中还没有或粗略地参数化了它。格陵兰岛的潮水冰川终止于约 600 至 800 米深的长峡湾，将冰盖边缘与陆架连接起来。冰川终点通常位于海平面以下数百米处，因此暴露在峡湾厚厚的水柱中。两名研究人员最近从格陵兰岛东南部的两个大型冰川峡湾收集的独特数据表明，这些峡湾全年充满来自北极的寒冷淡水和来自亚热带的温暖咸水，其不同的特性影响着冰缘环流。此外，船基和系泊速度测量表明，峡湾的特点是快速、高度变化、剪切流和剧烈的峡湾/陆架交换，这可能在将热量输送到冰川终点方面发挥了作用。这意味着海底融化速率取决于一系列海洋过程，包括外部强迫的峡湾环流、峡湾/陆架交换以及陆架上的属性分布。然而，这些过程如何影响海底融化速率或影响其变化的细节目前尚不清楚。该项目将通过将两个峡湾的船基和系泊数据分析与模型层次结构相结合来填补这一空白（实验室和数值）以确定控制峡湾特性和环流以及海洋/冰川界面海底融化速率的参数和机制。在确定了对海底融化速率的控制措施后，项目研究人员将利用历史海洋学和大气数据来确定在没有峡湾数据的情况下冰川加速之前时期的峡湾状况和海底融化速率。气候模型预测将用于估计未来海洋变化对格陵兰岛冰川海底融化的潜在影响。与出口冰川动力学、冰海边界物理学和峡湾环流方面的专家合作，将为这一本质上多学科的问题提供相关学科的专业知识和双向信息交换。拟议的工作旨在了解新发现的气候系统接线：海洋变化可以对格陵兰岛冰盖质量平衡产生快速而直接的影响。这是及时的，因为格陵兰岛正在发生巨大且不可预测的变化，并且相关的原因是气候和冰盖/冰川模型目前不存在冰盖/海洋相互作用。它是对南极洲周围冰盖/海洋相互作用的研究（两者中研究较多的一个）的补充，因为大规模的海洋环流和格陵兰岛狭窄而长的峡湾的存在都贡献了一套独特的相关动力机制。影响：这项工作旨在加深我们对气候系统中以前被忽视的重要联系的理解，这对我们准确预测海平面上升的能力具有深远的影响 - 这是一个严重而紧迫的社会关注问题。预计这项工作的结果将有助于将相关动态（即使是参数化形式）纳入未来的模型中，从而改善未来海平面预测。该工作计划涉及来自互补领域的几位国际专家，因此将有助于促进所涉及的多个学科之间和跨国界之间的互动。它涉及两名研究生和一名博士后，他们将接触前沿问题和多学科研究团队。该项目的结果将广泛传播给跨学科的科学家（正如 PI 长期组织暑期学校和工作组所证明的那样），并通过不同的媒体渠道向公众广泛传播（正如最近对研究人员格陵兰岛工作的报道所表明的那样）波士顿科学博物馆、纽约时报、天气频道和意大利国家电视台等场所。