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

北冰洋正在经历快速变化。这对战略和战术军事规划、区域乃至全球气候、北方生态系统和文化以及经济利益都具有重大意义。气候模型定性地认为，这些变化将持续下去。对具体基准的预测，如夏季北冰洋不结冰，几十年后才能达到。减少北极变化预测的不确定性是一项重要任务。该项目确定周期约为12小时的潮汐和近惯性(NI)波是北极海洋速度场、混合率和冰动力学的主要组成部分，目前在全球耦合气候模式中没有表现出来。该项目将在选定的海流计记录中为北极社区提供一个随时间变化的潮汐和NI能量数据库。此外，它还将提供一个经过仔细验证的、高分辨率、完全强迫的北极海/海-冰耦合模式(OIM)，用于量化高频(HF)过程对北冰洋及其冰盖的季节和较长期变化的影响。该项目将通过支持一名博士后助理和一名研究生的培训，以及通过支持两名职业生涯早期的科学家，为科技、经济和经济管理部门的劳动力发展作出贡献。在阿肯色州、德克萨斯州、华盛顿州和俄勒冈州的学校，将通过面对面和网络研讨会计划实现K-12的外展。将制作一个公众友好的视频，将模式结果可视化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。项目受到对海冰状态变化非常敏感的强烈高频洋流和冰流漂移速度的观测、对海洋混合和冰变形的高频时间序列的稀疏测量以及具有参数化潮汐强迫的粗格网模式的推动，该项目检验了以下假设：“高能的高频过程，包括潮汐和风生NI波，是北极三维水文和环流的季节性周期和长期趋势的关键因素，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。该计划的具体目标是绘制高频能量在整个北极海洋和冰中的随时间变化的分布图；评估高频过程在北冰洋和上层海洋中的作用；加深对耦合海冰、海洋和大气的高频过程的理解；并量化高频过程对季节周期和较长期趋势的影响。它利用快速增长的海洋和海冰速度数据库以及OIMs分辨率和物理真实性的改进，综合了对选定北冰洋系泊和海冰漂移数据的潮汐和NI信号的分析，验证了具有完全大气和潮汐强迫的高分辨率(~2公里×106垂直高度)泛北极OIM，并比较了一套在不同强迫下的模式模拟，以确定主要的HF过程。用简化的强迫(例如，去除潮汐和低通滤波风以减少NI强迫)的模拟将确定在季节性和更长时间尺度上高频对海洋和海冰状态的影响所涉及的关键因素。重点领域包括高频过程对冰层形成和扩散的影响，对河流淡水和陆架海热通量的影响，对北极大陆坡大西洋和太平洋来源水域混合的影响，对海洋和海冰高频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周期的影响。

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.