Collaborative Research: Three-dimensional structure of Arctic tides and near-inertial oscillations, and their role in changing the Arctic Ocean and ice pack

北冰洋正在经历迅速的变化。对战略和战术军事规划具有重要意义；区域性的，也许是全球性的气候；北方生态系统和文化；还有经济利益。气候模型定性地认为这些变化将持续下去。具体基准（如北冰洋夏季无冰）何时能达到的预测相差几十年。减少北极变化预估中的不确定性是一项重要任务。该项目确定潮汐和周期约为12小时的近惯性（NI）波是北冰洋速度场、混合率和冰动力的主要组成部分，而这些目前尚未在全球耦合气候模式中得到体现。该项目将为北极社区提供一个数据库，其中包含随时间变化的潮汐和NI能量，这些数据来自精选的海流仪表记录。此外，它将提供一个经过仔细验证的、高分辨率的、完全强迫的北极耦合海洋/海冰模型（OIM），用于量化高频（HF）过程对北冰洋及其冰盖的季节性和长期变化的影响。该项目将通过支持一名博士后助理和一名研究生的培训，以及支持两名早期职业科学家，为STEM劳动力的发展做出贡献。K-12外展将通过在AK、TX、WA和OR学校的面对面和网络研讨会项目来实现。将制作一个公众友好的视频，将模型结果可视化，并分发给学校和其他社区，包括阿拉斯加沿海村庄，并在项目网站上突出显示。基于对海冰状态变化非常敏感的强高频洋流和冰漂速度观测、海洋混合和冰变形高频时间序列的稀疏测量以及潮汐强迫参数化的粗网格模型，本项目验证了以下假设：“高能高频过程，包括潮汐和风产生的NI波，是北极三维水文和环流、海冰特征以及大气、海洋和海冰之间的热量、淡水和动量交换的季节性循环和长期趋势的关键因素。”该项目的具体目标是绘制整个北极地区海洋和冰层中高频能量随时间变化的分布图；评估高频过程在北极冰和上层海洋中的作用；加深对海冰、海洋和大气耦合HF过程的理解；并量化HF过程对季节周期和长期趋势的影响。利用快速增长的海洋和海冰速度数据库，以及OIMs分辨率和物理真实感的改进，它集成了对精选北冰洋系泊和海冰漂移数据的潮汐和NI信号的分析，验证了具有全大气和潮汐强迫的高分辨率（~2 km x 106垂直高度）泛北极OIM，并比较了一套具有不同强迫的模式模拟，以确定主要的HF过程。简化强迫（例如，去除潮汐和低通过滤风以减少NI强迫）的模拟将在季节性和更长的时间尺度上确定HF对海洋和海冰状态影响的关键因素。重点领域包括HF过程对陆架海的冰的形成和河流淡水的分散以及热通量的影响，对沿北极大陆斜坡的大西洋和太平洋来源的水的混合的影响，对海洋和海冰HF过程之间的反馈的影响，以及对大气与海洋和海冰热交换的季节性循环的影响。

The Arctic Ocean is undergoing rapid change. Implications are significant for strategic and tactical military planning; regional, and perhaps global, climate; northern ecosystems and cultures; and economic interests. Climate models qualitatively agree that these changes will persist. Projections of when specific benchmarks, such as an ice-free summer Arctic Ocean, will be reached vary by several decades. Reducing uncertainty in Arctic change projections is an important task. This project identifies tides and near-inertial (NI) waves, with periods of approximately 12 hours, as the major components of Arctic ocean velocity fields, mixing rates and ice dynamics that are not presently represented in global coupled climate models. The project will provide the Arctic community with a database of time-dependent tidal and NI energy in select current meter records. Also, it will provide a carefully-validated, high-resolution, fully-forced Arctic coupled ocean/sea-ice model (OIM) for quantifying the effects of high-frequency (HF) processes on seasonal and longer-term variability of the Arctic Ocean and its ice pack. The project will contribute to STEM workforce development through support for the training of a post-doctoral associate and a graduate student, and through support for two early-career scientists. K-12 outreach will be enabled through in-person and webinar programs at schools in AK, TX, WA and OR. A public-friendly video with visualization of model results will be prepared and distributed to schools and other communities including coastal Alaskan villages, and highlighted on the project website.Motivated by observations of strong HF ocean currents and ice drift velocities that are very sensitive tochanges in sea-ice state, sparse measurements of HF time series of ocean mixing and ice deformation,and coarse-grid models with parameterized tide forcing, this project tests the following hypothesis: "Energetic, HF processes, including tides and wind-generated NI waves, are critical contributors to the seasonal cycle and longer-term trends of the Arctic's 3-D hydrography and circulation, sea-ice characteristics, and exchanges of heat, freshwater and momentum between the atmosphere, ocean and sea-ice." The program's specific goals are to map the time-dependent distribution of HF energy in the ocean and ice throughout the Arctic; assess the role of HF processes in the Arctic ice and upper ocean; develop understanding of the HF processes coupling the sea ice, ocean, and atmosphere; and quantify the effect of HF processes on seasonal cycles and longer-term trends. Taking advantage of rapidly growing databases for ocean and sea-ice velocities, and improvements in resolution and physical realism of OIMs, it integrates analyses of tidal and NI signals in select Arctic ocean moorings and sea-ice drift data, validation of a high resolution (~2 km x 106 vertical levels) pan-Arctic OIM with full atmospheric and tidal forcing, and comparison of a suite of model simulations with different forcing to identify dominant HF processes. Simulations with simplified forcing (e.g., removing tides and low-pass filtering the winds to reduce NI forcing) will identify key factors involved in HF influence on ocean and sea-ice state on seasonal and longer time scales. Focus areas include the effect of HF processes on ice formation and dispersion of river freshwater and heat fluxes in shelf seas, on mixing of Atlantic- and Pacific-sourced waters along the Arctic continental slopes, on feedbacks between ocean and sea-ice HF processes, and on the seasonal cycle of atmospheric heat exchange with the ocean and sea ice.