Collaborative Research: A field and laboratory study of the melting processes of icebergs in a Greenland fjord

合作研究：格陵兰峡湾冰山融化过程的现场和实验室研究

• 批准号: 1657938
• 负责人: Hanumant Singh
• 金额: $ 4.31万
• 依托单位: Northeastern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-15 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1657938&HistoricalAwards=false
• 关键词: Collaborative; Research; field; laboratory; study

Iceberg calving accounts for half of the mass discharge from the Greenland and Antarctic ice sheets, which has increased dramatically over the last two decades. Through their displacement and progressive melt, these icebergs impact the regional ocean and its ecosystem by affecting its stratification, nutrient and carbon cycling. Freshwater input due to iceberg melt has the potential to impact regional sea-ice distribution and the global overturning circulation. In addition, they pose a threat to local infrastructure and navigation. Notwithstanding their importance, our understanding of where and how icebergs melt is limited and their representation in ocean and climate models is over-simplistic, in part because informed by only a handful of observations. As a result, model-based predictions of iceberg melt rates, of the fate of the melt water, and of its impact on the ocean are highly uncertain. Improved iceberg parameterizations will reduce uncertainties in model-based predictions of the impact of shrinking polar ice caps on the large-scale ocean circulation and marine ecosystems. This is an urgent issue given the projected increase in iceberg discharge from both ice sheets. While the field experiment will take place in Greenland, it is expected that the results will be applicable to Antarctica?s tabular icebergs. One student supported by this project will be exposed to a cutting-edge problem and a multidisciplinary team of researchers. A video package, created by professional producers with experience in educational/environmental material, will be developed as part of this project to illustrate the different methodologies used to address a complex scientific problem and engage a broad audience. The package produced here will include a similar video-documentary, a 360-degree virtual reality video and clips to be distributed to various media venues including social media. In general, the diverse scientific team engaged in this project has an extensive track record of public outreach through media engagement.Current parameterizations of iceberg motion and melt in ocean models typically utilize only surface ocean velocities and properties. This is inconsistent with the notion that much of the iceberg mass flux is concentrated in large icebergs with drafts of several hundred meters. Indeed, recent work by the investigators and others, based on observations, theory and laboratory experiments, has shown that both the motion and the melting of deep-keeled icebergs in a stratified ocean characterized by a vertically sheared flow are not well represented by current parameterizations. While incorporating the impact of sheared flows on parameterizations of iceberg motion is fairly straightforward, the impact of sheared flows on iceberg melt is not. In particular, preliminary laboratory experiments show that the interaction of the sheared flow with the melt plumes that rise at the edge of icebergs is complex - giving rise to non-linear melt responses. Similarly, observations and models of glaciers melting in a stratified ocean have shown that the melt dynamics is strongly affected by the ambient stratification. Based on these recent studies, the hypothesis that melting of icebergs and the distribution of melt water, in the vicinity of the iceberg, are strongly affected by the ambient stratification and vertical shear will be tested. Through a multi-faceted approach that includes field measurements in Greenland and laboratory modeling, this project seeks to identify the leading parameters that impact the distribution of subsurface melt of an iceberg and the release of melt water into the surrounding ocean. An autonomous surface vehicle, the jetyak, and an unmanned aerial vehicle will be used to quantify iceberg melt and map the circulation and distribution of melt water around the iceberg. Idealized laboratory experiments will complement the field measurements and provide quantitative and comprehensive descriptions of the melt. Together, these results will be used to improve iceberg parameterizations to be used in ocean and climate models.

冰山崩解占格陵兰和南极冰盖质量排放的一半，在过去二十年中急剧增加。这些冰山通过移位和逐渐融化，影响区域海洋及其生态系统，影响其分层、营养和碳循环。冰山融化造成的淡水输入有可能影响区域海冰分布和全球翻转环流。此外，它们还对当地的基础设施和航行构成威胁。尽管它们很重要，但我们对冰山在哪里以及如何融化的理解是有限的，它们在海洋和气候模型中的代表性过于简单，部分原因是只有少数观察结果。因此，基于模型的冰山融化速度、融化水的命运及其对海洋的影响的预测是高度不确定的。改进冰山参数化将减少基于模型预测极地冰盖缩小对大规模海洋环流和海洋生态系统影响的不确定性。这是一个紧迫的问题，因为预计来自两个冰盖的冰山流量将增加。虽然实地实验将在格陵兰岛进行，但预计结果将适用于南极洲。扁平的冰山。一个学生通过这个项目的支持将接触到一个前沿的问题和研究人员的多学科团队。作为该项目的一部分，将制作一套录像，由在教育/环境材料方面有经验的专业制作人制作，以说明用于解决复杂科学问题的不同方法，吸引广大观众。在这里制作的节目将包括一个类似的视频纪录片，一个360度虚拟现实视频和剪辑，将分发到包括社交媒体在内的各种媒体场所。一般而言，参与该项目的多元化科学团队通过媒体参与进行了广泛的公众宣传，目前海洋模型中冰山运动和融化的参数化通常只利用表面海洋速度和属性。这与大部分冰山质量通量集中在具有数百米吃水深度的大型冰山的概念不一致。事实上，调查人员和其他人最近根据观察、理论和实验室实验开展的工作表明，在以垂直剪切流为特征的分层海洋中，目前的参数化方法不能很好地反映深龙骨冰山的运动和融化。虽然将剪切流对冰山运动的参数化的影响相当简单，但剪切流对冰山融化的影响却不是。特别是，初步的实验室实验表明，剪切流与冰山边缘上升的熔体羽流的相互作用是复杂的-引起非线性熔体响应。同样，对分层海洋中冰川融化的观测和模型表明，融化动态受到环境分层的强烈影响。基于这些最新的研究，假设冰山融化和融水的分布，在冰山附近，强烈影响的环境分层和垂直剪切将进行测试。通过多方面的方法，包括在格陵兰岛的实地测量和实验室建模，该项目旨在确定影响冰山地下融化分布和融化水释放到周围海洋的主要参数。一个自主的水面车辆，jetyak和一个无人驾驶飞行器将被用来量化冰山融化，并绘制冰山周围融水的循环和分布。理想化的实验室实验将补充现场测量，并提供定量和全面的熔体描述。总之，这些结果将用于改进海洋和气候模型中使用的冰山参数化。