Collaborative Research: Ideas Lab: BLUES: Boundary Layer Under-ice Environmental Sensing

全球气候变化正在推动地球表面各种形式的冰融化，并导致全球海平面上升。虽然冰融化的证据是世界范围的，例如海冰范围的缩小、极地冰架的损失和每年湖冰覆盖的减少，但由于实地数据有限和对冰厚度的相对粗糙的测量，冰融化的速度很难量化。冰厚测量是通过传播声波信号通过冰，作为衰减特性和整体冰厚的函数，分辨率下降。新型声学超材料将用于“创意实验室：工程技术推进水下科学”（ETAUS）项目，以开发一种变革性的技术工具，可以提供远距离、高分辨率的冰厚测量，并提供一种新的机制来成像冰的内部结构。这些高分辨率的观测结果将用于通过观察时间的变化来改进全球冰融化的估计。最初的测试和开发将在实验室环境中进行，然后在声学信号衰减特性可变的天然湖冰上进行验证。在每个阶段，将以数值模拟为指导进行开发和实验演示。这一已开发的仪器将对从北极到南极的冰冻圈内所有形式的冰的科学认识产生革命性的影响。虽然极地地区处于气候变化的最前沿，但它们也是地球上最难以进入的地区之一，公众很难参与其中。为此，将在太浩环境研究中心的教育和推广小组的帮助下开发新的教育材料，这将有助于扩大公众对湖泊科学和工程的参与。为了有效地监测和预测与气候相关的变化，在冰下科学界的所有学科中，一个关键的科学需求是准确测量冰/水界面的冰的增加和融化速度，然后利用这些信息来生成更好的冰下水循环和混合模型。然而，现有技术受到成像能力、测量分辨率和体积的限制，阻碍了它们在科学发现中的应用。为了解决这些限制，本项目将开发一种新的超材料增强声相控阵（MEAPA）系统，并探索该系统在高分辨率冰融化估计中的应用。将研究渐变折射率声学超材料，以提供改进的聚焦、波束导向和准直特性，从而在较薄的冰层中实现高分辨率成像（亚波长分辨率），并进一步提高MEAPA系统在较厚冰层中的探测范围。开发的MEAPA系统将在实验室和现场环境中进行表征和验证。然后，它将用于更好地参数化底部粗糙度，并将数据与三维水动力模型中的湖冰边界层动力学观测相耦合。将该仪器的工程开发与极地冰群落的科学需求相结合，将为极地环流模式（GCM）的子网格过程提供信息。最终，这个系统将使我们能够用精确的模型更好地预测冰的增长和融化，并更好地量化南极湖冰到冰架的质量增加和损失。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Global climate change is driving all forms of ice to melt from the Earth’s surface and contribute to global sea-level rise. While evidence of ice melt is worldwide, such as decreasing sea-ice extent, loss of ice shelves in polar regions and a reduction in annual lake-ice coverage, ice melt rates are poorly quantified, resulting from limited field data and relatively coarse measurements of ice thickness. Ice thickness measurements, made by propagating acoustic signals through the ice, decrease in resolution as a function of the attenuation properties and overall ice thickness. Novel acoustic metamaterials will be used in this Ideas Lab: Engineering Technologies to Advance Underwater Sciences (ETAUS) project to develop a transformative technology tool that can provide long-range, high-resolution measurements of ice thickness and provide a new mechanism to image the internal structure of the ice. These high-resolution observations will be used to refine global estimates of ice melt by looking at changes through time. Initial testing and development will be conducted in a laboratory setting before validation on natural lake ice that is variable in its acoustic signal attenuation properties. In every phase, the development and experimental demonstration will be guided by numerical modeling. This developed instrument will be transformative in terms of scientific understanding of all forms of ice within the cryosphere from the Arctic to the Antarctic. While polar regions are at the forefront of climate change, they are also some of the least accessible areas of the planet and make it difficult for the public to engage. To this end, new educational materials will be developed with the help of the education and outreach team at the Tahoe Environmental Research Center, which will be used to help broaden public participation in lake science and engineering.To effectively monitor and predict climate-related changes, a key scientific need in all disciplines of the under-ice scientific community is to accurately measure ice accretion and melt rates at the ice/water interface, then use that information to generate better models of under-ice water circulation and mixing. However, existing technologies are limited by their imaging capabilities, measurement resolutions, and bulky sizes, which hinder their applications for scientific discovery. To address these limitations, this project will develop a new metamaterial-enhanced acoustic phased array (MEAPA) system and to explore the application of this system for high-resolution estimations of ice melt. Graded index acoustic metamaterials will be investigated to provide improved focusing, beam steering, and collimation properties to achieve high-resolution imaging (subwavelength resolution) in thinner ice and to further enhance the detection range of the MEAPA system in thicker ice. The developed MEAPA system will be characterized and validated in laboratory and field settings. Then, it will be used to better parameterize bottom roughness, and the data will be coupled to boundary layer dynamics observations of lake ice in three-dimensional hydrodynamic models. Coupling the engineering development of this instrument with the scientific need of the polar ice community will inform subgrid processes of General Circulation Models (GCM) for polar regions. Ultimately, this system will enable us to better predict ice growth and melt with accurate models and to better quantify mass gain and loss from lake ice to ice shelves in Antarctica.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.