Snow property characterization for improved radar altimetry estimates of sea ice thickness

雪特性表征，以改进雷达测高法估计海冰厚度

• 批准号: RTI-2020-00182
• 负责人: Yackel, John
• 金额: $ 9.64万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Research Tools and Instruments
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=693446
• 关键词: Snow; property; characterization; improved; radar

Earth's climate is experiencing unprecedented change and monitoring and predicting the nature of this change is an ongoing global scientific endeavor. Inclusion of sea ice in global climate models is paramount due to its control on heat transfer between the atmosphere and ocean. For example, with less sea ice, more ocean heat can transfer to the Arctic atmosphere, leading to further warming and less sea ice, a particularly damaging positive feedback loop. Arctic sea ice extent has declined by 13% and thinned by nearly 40% over the past four decades as estimated from satellites, with the Arctic Ocean predicted to become ice free in summer for the first time before 2050. Today, more than 80% of the Arctic sea ice cover is composed of seasonal sea ice. Considerable uncertainty remains as to how these changes will influence the Arctic marine ecosystem, Arctic and mid-latitude climates and ecosystems, socio-economic issues such as pan-Arctic shipping and cruise tourism, and the livelihood of indigenous communities including those in northern Canada. The snow cover on sea ice is a critical component of snow/sea ice system because it controls the ice accretion and ablation rate due to its relatively small thermal conductivity. Because of the high albedo of snow, shortwave radiative exchanges dominate the sea ice-albedo' feedback mechanism and act to insulate the sea ice from the warming atmosphere during the spring to summer transition. As a result, the snow cover ultimately controls sea ice thickness and subsequent melt behavior and largely determines the mechanical strength properties which control sea ice summer break-up potential. The accuracy of pan-Arctic sea ice thickness estimates from satellite remote sensing depends on the performance of statistical thresholding methods using radar altimetry to distinguish sea ice floes from sea ice leads and open water. However, these simple methods do not fully account for seasonally and spatially varying complex geophysical processes in the snow cover on sea ice, which affect radar propagation and add considerable error and uncertainty to estimates. These salient variables include snow depth, snow density, snow grain size and specific surface area, snow electrical properties including liquid water and snow brine content. New and improved geophysical instrumentation developed in recent years now permits characterization of these key snow variables with significantly improved accuracy. The instrumentation suite described in this proposal will significantly improve performance of dielectric and microwave scattering models for assessment of radar altimetry estimates of snow thickness on sea ice. This proposal also describes the urgency for a suite of state-of-the-art snow geophysical instrumentation and an HQP data collection focused plan towards improved snow geophysical property measurements towards Arctic-wide improvements to sea ice thickness estimates from radar altimetry. *****************

地球的气候正经历前所未有的变化，监测和预测这种变化的性质是一项持续的全球科学努力。在全球气候模型中纳入海冰，这是由于其控制着大气和海洋之间的传热而至关重要的。例如，随着海冰的较少，更多的海洋热量可以转移到北极气氛中，从而导致进一步的变暖和更少的海冰，这是一个特别有害的积极反馈回路。从卫星估计，在过去的四十年中，北极海冰范围下降了13％，并减少了近40％，预计北极海洋将在2050年之前首次在夏季自由冰。这些变化将如何影响北极海洋生态系统，北极和中纬度气候和生态系统，社会经济问题，例如泛阿亚尔亚式运输和巡游旅游，以及包括北加拿大北部的土著社区的生计，仍然存在很大的不确定性。海冰上的雪覆盖是雪/海冰系统的关键组成部分，因为它由于其导热率相对较小而控制着冰的积聚和消融速率。由于雪的反照率很高，短波辐射交流主导了海冰 - 阿尔贝托的反馈机制，并在春季到夏季过渡时采取行动使海冰与温暖气氛隔离开来。结果，雪覆盖最终控制了海冰厚度和随后的熔体行为，并在很大程度上决定了控制海冰暑期破裂潜力的机械强度。卫星遥感的泛氧化海冰厚度估算的准确性取决于使用雷达高度测定法将海冰与海冰铅和开放水分区分开的统计阈值方法的性能。但是，这些简单的方法并不能完全解释海冰上的雪覆盖中的季节性和空间上复杂的地球物理过程，这会影响雷达传播，并为估计值增加了相当大的错误和不确定性。这些显着的变量包括雪深，雪密度，雪粒尺寸和特定的表面积，包括液态水和雪盐含量在内的雪地电特性。近年来开发的新的和改进的地球物理仪器允许对这些关键的雪变量进行表征，并具有显着提高的精度。该提案中描述的仪器套件将显着改善介电和微波散射模型的性能，以评估海冰上雪厚的雷达高度测定估计。该提案还描述了一套最先进的雪地地球物理仪器和HQP数据收集计划的紧迫性，以改善积雪地球物理性能测量，以改善北极范围的改进，从而改善了雷达高度测定的海冰厚度估计。 *****************