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: 1129895
• 负责人: Thomas Haine
• 金额: $ 29.32万
• 依托单位: Johns Hopkins University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2016-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1129895&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.

知识分子的优点：格陵兰冰川的潜艇融化已成为冰盖的质量平衡中的关键术语，并且是它们最近加速的合理触发因素，这有助于将格陵兰岛对海平面上升的贡献增加一倍。尽管它的重要性，但我们对海底熔化的理解是有限的，目前在冰川，冰盖和气候模型中缺乏或粗鲁的参数化。格陵兰的潮汐水冰川以大约600至800 m深的峡湾结束，将冰盖的边缘连接到架子上。冰川末端通常以海平面以下数百米的速度接地，因此，将其暴露于峡湾水柱的厚部分。最近由两名研究人员收集的独特数据是从东南格陵兰东南部的两个大冰川峡湾收集的，这些数据全年都充满了北极起源的冷，新鲜的水和亚热带起源的温暖而咸的水，其不同的特性会影响冰上的循环。此外，基于船舶和停泊的速度测量值表明，峡湾的特征是快速，可变，剪切的流量和剧烈的峡湾/架子交换，可能在将热量运送到冰川末端中起作用。这意味着海底熔体速率取决于一套海洋过程，包括外部强迫峡湾循环，峡湾/架子交换以及货架上的财产分布。然而，目前未知这些过程如何有助于下海底融化的速率或影响其可变性的细节。该项目将通过将两个峡湾的基于船舶的基于船舶的和停泊数据的分析与模型（实验室和数值）的层次结合结合，以确定在幻影和范围内融合速率和旋转速度和频率的范围和旋转速度的层次。在确定了海底熔体速率的控件后，项目调查人员将使用历史海洋学和大气数据来确定冰川加速之前的峡湾条件和海底熔体速率，如果没有峡湾数据可用。气候模型预测将用于估计未来海洋变异性对格陵兰冰川海底融化的潜在影响。与出口冰川动力学，冰山边界和峡湾循环的物理学的专家合作将提供相关学科的专业知识，并为此内部多学科问题提供双向信息交换。提出的工作旨在了解气候系统的新发现的接线：海洋变异性可以对格陵兰的冰盖质量平衡产生快速而直接的影响。这是因为冰盖/海洋相互作用目前在气候和冰盖/冰川模型中不存在冰盖/海洋相互作用，因此及时发生了较大且无关紧要的变化。 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直接的社会关注。可以预期，这项工作的结果将有助于在未来模型中纳入相关的动态（即使以参数化形式），因此可以改善未来的海平面预测。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与国家边界之外的互动。它涉及两名研究生和一名大约一名，他们将面临一个尖端的问题和多学科研究人员团队。正如PIS组织暑期学校和工作组的PIS长途旅行所证明的那样，该项目的结果将被广泛地传播给跨学科的科学家，以及通过不同的媒体媒体向公众传播，如最近在包括波士顿，纽约时报，天气频道和Italian全国电视台的Greenland著作的报道所示，包括研究人员在包括波士顿科学博物馆的场地上。