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Decadal and multi-decadal ocean memory in the eddying regime

涡流状态下的十年和多年代海洋记忆

基本信息

批准号：
1258887
负责人：
Paola Cessi
金额：
$ 85.87万
依托单位：
University of California-San Diego Scripps Inst of Oceanography
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2013
资助国家：
美国
起止时间：
2013-04-01 至 2018-03-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1258887&HistoricalAwards=false
关键词：
Decadal multi decadal ocean memory

项目摘要

Climate predictions on decadal scales have proven elusive. On these time-scales, the natural chaotic variability of the climate system dominates over the more predictable trends due to anthropogenic climate forcing. The differences among coupled general circulation models results are discouraging, and point to a lack of convergence in spatial resolution and to inadequate physical parameterizations. The difficulty is compounded by the short duration of observational records of the climate system, particularly those of the ocean and cryospherewhich hinders robust statistical analysis on decadal time scales.A leading candidate for pockets of predictability in selected regions resides in the memory intrinsic in the slow, almost adiabatic evolution of the ocean below the mixed layer. The periodic reemergence of oceanic temperature anomalies in winter is a potential source of predictability on scales longer than one year. In order for this mechanism to provide robust interaction with the atmosphere, ocean temperature anomalies must survive the seasonal cycling and the eddy stirring on isopycnals. It is conjectured that temperature perturbations on scales larger than the eddy size survive isopycnal eddy stirring. The threshold amplitude and duration (or persistence) of perturbation that can withstand the seasonal cycling must be determined.Intellectual Merit: This project will identify the regions in the Atlantic Ocean that can enhance decadal predictability in the extra-tropics. The focus on adiabatic subsurface flow in the eddying regime will complement the traditional approach of studying diffusive, highly damped oceanic dynamics, and will identify the most robust oceanic physical processes for prediction at decadal scales. The Atlantic Ocean is chosen because in this region the natural time scales are decadal, through the wind-gyres dynamics, and multi-decadal, through the pole-to-pole overturning circulation. It is essential to work in the eddying regime, because mesoscale eddies determine the sub-thermocline oceanic stratification and thus the oceanic heat transport. Furthermore, at high resolution, damping is reduced allowing large regional gradients and longer duration of influence: both are necessary elements for robust atmospheric imprinting. The approach is to use several ocean models spanning a range of complexities: coarse resolution forward and adjoint models both with parameterized baroclinic eddies, and a model at eddy-resolution.Broader Impacts: The economical and social benefits of climate information for periods longer than a season and regions beyond the tropics cannot be overstated. Mid- and high-latitude ocean processes have the potential to provide skill to decadal forecasts, and they are the focus of this proposal. A graduate student and an early-career scientist will enrich their knowledge in physical oceanography, climate dynamics and the scientific method, and be trained in mathematics, numerical modeling and modern scientific computations. A middle and high school teacher workshop will contribute to informing the new generation of citizens on the achievements, limitations and future prospects of climate science.

十年尺度的气候预测已被证明是难以捉摸的。在这些时间尺度上，由于人为气候强迫，气候系统的自然混沌变率在更可预测的趋势上占主导地位。耦合的一般环流模式结果之间的差异令人沮丧，并指出在空间分辨率上缺乏收敛和物理参数化的不足。气候系统的观测记录，特别是海洋和冰冻圈的观测记录的持续时间很短，妨碍了对年代际时间尺度进行可靠的统计分析，这使困难更加严重。在特定区域的可预测性的一个主要候选存在于混合层以下海洋缓慢的、几乎绝热的演化所固有的记忆中。冬季海洋温度异常的周期性重现是一年以上尺度上可预测性的一个潜在来源。为了使这一机制与大气提供强有力的相互作用，海洋温度异常必须经受住季节循环和等平行线上的涡旋搅拌。据推测，温度扰动在大于涡旋尺寸的尺度上仍然存在于等压涡旋搅拌中。必须确定能够承受季节性循环的扰动的阈值幅度和持续时间（或持久性）。知识价值：该项目将确定大西洋中可以提高温带年代际可预测性的区域。对涡旋状态下绝热地下流的关注将补充研究扩散、高阻尼海洋动力学的传统方法，并将确定在年代际尺度上进行预测的最强大的海洋物理过程。之所以选择大西洋，是因为该地区的自然时间尺度是年代际的，通过风环流动力学，以及多年代际的，通过极对极翻转环流。在涡旋状态下工作是必要的，因为中尺度涡旋决定了亚温跃层海洋分层，从而决定了海洋热输送。此外，在高分辨率下，阻尼减少，从而允许较大的区域梯度和更长的影响持续时间：这两者都是强大的大气印记的必要因素。方法是使用几种复杂程度不同的海洋模型：具有参数化斜压涡旋的粗分辨率正演和伴随模型，以及涡旋分辨率的模型。更广泛的影响：超过一个季节和热带以外地区的气候信息的经济和社会效益怎么强调都不为过。中高纬度海洋过程有可能为十年预测提供技术，它们是本建议的重点。研究生和早期科学家将丰富他们在物理海洋学、气候动力学和科学方法方面的知识，并接受数学、数值模拟和现代科学计算方面的训练。初中和高中教师讲习班将有助于向新一代公民宣传气候科学的成就、局限性和未来前景。