Monitoring Sea Ice Evolution with Ultrawideband Microwave Radiometry in the MoSAIC Campaign

北极的演变是关乎地球未来的一个关键问题。一个关键的方面是了解大气，海洋和海冰的过程如何相互作用并影响北冰洋海冰的行为和分布。作为北极气候研究多学科漂流观测站（MOSAiC）活动的一部分，该项目正在部署一个超宽带微波辐射计，以提高远程确定海冰厚度信息的能力。MOSAiC将RV北极星号（RV Polarstern）部署到北极浮冰中，为期一年，可获得长期海冰测量数据，再加上将获得的广泛的冰、海洋和大气现场测量数据，为海冰监测研究提供了最佳环境，从而实现更好的海冰演变模型。这些模型对于推进北极系统科学和预测北极的未来至关重要。通过培养下一代极地科学和观测研究人员，学生培训也将产生社会影响。北极的艰苦条件及其空间异质性强迫促使卫星或机载平台进行远程地球观测。遥感系统已证明在监测海冰范围和部分覆盖以及在较小程度上监测海冰厚度和类型方面是有效的。目前的l波段（1.4 ghz）微波辐射计和激光测高仪对0.5至2米冰厚的灵敏度有限，与较厚的多年冰相比，这种情况越来越普遍。感知海冰温度和盐度特性的能力，特别是它们在冰本身内部的变化，也可以为理解冰的形成和溶解提供重要的新好处。作为MOSAiC中央天文台的一部分，该项目部署了一个四通道超宽带微波辐射计，观测范围为0.5至2 GHz，以获取冰热发射及其随厚度和其他冰性质变化的独特数据集。通过测量海冰在多个频率下的热辐射，以及低于1.4 GHz的频率，将有可能获得更多关于冰的性质和更深入的信息。所获得的测量结果将进一步发挥重要作用，在其他MOSAiC项目研究人员获得的现场测量结果和大约9米× 26米的仪器足迹之间架起桥梁，该仪器足迹将提供与浮冰相关的“中间”尺度上的平均冰特性。这个为期三年的项目包括第一年的仪器准备和规划，第二年的活动参与（包括在MOSAiC第一和第二阶段的项目人员配备），以及第三年的广泛数据分析。通过加深对海冰在点（原位）和流量尺度之间的空间尺度的理解，该项目将为实现海冰预测模型中的“亚网格尺度”现象参数化提供重要的环节。所获得的厚度、盐度和温度的时间历史也将成为表征相关空间尺度上海冰能量收支的重要数据集。在被动微波遥感应用方面取得的进展也将为海冰的电磁特性提供新的见解，用于未来开发新的仪器和卫星观测方法。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。

The evolution of the Arctic is a key question for the future of our planet. One key aspect is to understand how processes in the atmosphere, ocean, and sea ice interact and affect Arctic ocean sea ice behavior and distribution. As part of the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) campaign, this project is deploying an ultra-wideband microwave radiometer to improve the ability to remotely determine sea ice thickness information. The long term measurements of sea ice available from MOSAiC's one year deployment of the RV Polarstern into an Arctic ice floe, combined with the extensive ice, ocean, and atmosphere in-situ measurements to be acquired, provide an optimal environment for sea ice monitoring studies, which in turn enable better models of sea ice evolution. Those models are criticall important to advancing Arctic system science and predicting the future of the Arctic. Student training will also provide societal impact by preparing the next generation of researchers in polar science and observation.The difficult conditions of the Arctic along with its spatially heterogeneous forcing motivate remote Earth observations from satellites or airborne platforms. Remote sensing systems have proven to be effective in monitoring sea ice extent and fractional cover, as well as sea ice thickness and type to a lesser extent. Current L-band (1.4-GHz) microwave radiometers and laser altimeters have limited sensitivity to ice thickness in the range from 0.5 to 2 meters, which is increasingly common as compared to thicker multi-year ice. An ability to sense sea ice temperature and salinity properties, and particularly their variations within the ice itself, could also provide important new benefits for understanding ice formation and dissolution.The project is deploying a four channel ultra-wideband microwave radiometer observing from 0.5 to 2 GHz as part of the MOSAiC central observatory in order to acquire a unique dataset of ice thermal emissions and their variations with thickness and other ice properties. By measuring thermal emissions from sea ice at multiple frequencies, and frequencies lower than 1.4 GHz, more information on ice properties, and to greater depth, will be possible. The measurements acquired will further play an important role in bridging between the point in situ measurements to be acquired by other MOSAiC program investigators and the approximately 9 m x 26 m instrument footprint that will provide ice properties averaged over the "intermediate" scales associated with ice floes. The three year project includes instrument preparation and planning in year one, campaign participation in year 2 (including staffing by project personnel during MOSAiC legs I and II), and extensive data analysis in year 3.By advancing understanding of the spatial scaling between sea ice properties at point (in situ) and floe scales, the project will provide an important link to enable "sub-grid-scale" phenomena parameterization in sea ice forecast models. The time histories of thickness, salinity, and temperature acquired will also represent important datasets for characterizing the sea ice energy budget over relevant spatial scales. The advancement achieved in the use of passive microwave remote sensing will also provide new insights into the electromagnetic properties of sea ice for use in future development of new instrumentation and satellite observation methods.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.