Collaborative Research: Using ocean data assimilation to explore Arctic/subarctic climate variability

学术价值：近几十年来，高纬度气候发生了深刻的变化。该项目针对这些变化实现了两个目标。第一个目标是通过将数据同化应用于气象和海洋测量的稀疏历史记录，提高对过去一个世纪在高纬度地区发生的海洋变化的理解。与此目标相关的第一项任务将是改进简单海洋数据同化（SODA）数据同化海洋再分析作为高纬度研究的工具。这项任务直接建立在由该赠款的前身资助的工作的基础上。这种特殊的高纬度努力是必要的，因为该地区的复杂性。美国的地形、水团和海流、稀疏、不均匀的海洋和气象观测网，以及海冰和盐化过程的重要作用。第二项任务将是探索历史数据采样和地面气象学的限制，通过测试大洋再分析的可信度的实验来了解过去的气候变率。第二个目标是检验这些结果，以探索控制高纬度海洋、低纬度海洋和上覆大气之间相互作用的过程，以及这些相互作用如何可能导致气候变率。北欧海和北极在过去十年中经历的显著变暖与20世纪20年代至30年代的温暖期相似。这两个时期在量级上和对北大西洋次极区及上覆大气的影响上有多相似？在较短的年代际时间尺度上，流入北欧海的大西洋水显示出大量的变化，部分与气象的大尺度模式有关。与此相关的是地表盐度异常，如大盐度异常。这种变化的起源是什么？它与大气的关系是什么？它对气候的意义是什么？要实现第二个目标，就需要利用同化研究的结果作为指导，在耦合的大气/海洋/冰模式中探索这些机制，特别是在新的ipcc级模式运行中。耦合气候模型具有完整的物理特性，允许跟踪诸如淡水和热量等属性在气候系统中的运动，而与SODA和历史观测的比较提供了关于模型真实性的信息。更广泛的影响：该项目将通过发展和传播改进的SODA海洋再分析以及改进对其不确定性的理解，为科学界提供对高纬度海洋上层温度、盐度和环流过去变化的改进分析。这个项目吗?美国参与北冰洋模式相互比较项目和其他场所将有助于提高对海洋再分析的认识和使用，特别是SODA。本研究项目的第二部分，提高对海洋盆地交换作用的理解是一个需要了解的过程，以便开发预测模型。该项目将通过将数据集、分析和作为这项工作的一部分开发的计算机资源免费提供给系里的研究生，从而具有实质性的教育成分。

Intellectual merit: Recent decades have seen profound changes in higher latitude climate. This project addresses two goals responding to these changes. The first goal is to develop improved understanding of what past oceanic changes have occurred at high latitude during the past century through application of data assimilation to the sparse historical record of meteorological and oceanic measurements. The first task associated with this goal will be to improve the Simple Ocean Data Assimilation (SODA) data assimilation ocean reanalysis as a tool for high latitude research. This task builds directly on work funded by the predecessor to this grant. This special high latitude effort is required because of the complexities of the region?s topography, water masses and currents, the sparse, inhomogeneous oceanic and meteorological observational network, and the important role of sea ice and haline processes. The second task will be to explore the limits the historical data sampling and surface meteorology place on what can be learned about past climate variability through experiments testing the credibility of long ocean reanalyses.The second goal is to examine these results to explore the processes governing interaction between the high latitude ocean, the lower latitude ocean, and the overlying atmosphere, and how these interactions may contribute to climate variability. The remarkable warming the Nordic Seas and Arctic has experienced in the last decade bears similarity to a warm period in the 1920s-1930s. How similar are these two periods, both in magnitude and in impact on the subpolar North Atlantic and on the overlying atmosphere? On shorter decadal timescales the Atlantic Water flowing into the Nordic Seas shows substantial variability partially related to large-scale patterns in meteorology. Related to this are the anomalies of surface salinity such as the Great Salinity Anomaly. What is the origin of this variability, its relationship to the atmosphere, and what is its climate significance? Addressing this second goal will require exploring these mechanisms in coupled atmosphere/ocean/ice models, and in particular the new IPCC-class model runs, using the results of the assimilation studies as guidance. Coupled climate models have complete physics that allow the tracking of the movement of properties such as freshwater and heat through the climate system, while the comparisons to SODA and the historical observations provides information about the realism of the models.Broader impacts: This project will provide the scientific community with an improved analysis of past changes in the upper ocean temperature, salinity, and circulation at high latitude through development and dissemination of an improved SODA ocean reanalysis and improved understanding of its uncertainties. The project?s involvement in the Arctic Ocean Model Intercomparison Project and other venues will help promote the greater knowledge and use of ocean reanalyses generally, and SODA in particular. The second part of this research project, improving understanding of the role of oceanic basin exchanges is a process that needs to be understood in order to develop predictive models. The project will have a substantial educational component by making the data sets, analyses, and computer resources developed as part of this work freely available to the graduate students in the department.