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

学术价值：近几十年来，高纬度地区的气候发生了深刻的变化。该项目针对这些变化提出了两个目标。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，更好地了解过去一个世纪高纬度地区发生的海洋变化。与此目标相关的首要任务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该赠款的前身资助的工作的基础上。由于该地区地形、水团和洋流的复杂性、海洋和气象观测网络的稀疏、不均匀以及海冰和盐碱过程的重要作用，需要在高纬度地区开展这项特殊的工作。第二个任务是通过测试长期海洋再分析可信度的实验，探索历史数据采样和地面气象学对过去气候变化的了解的局限性。第二个目标是检查这些结果，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影响气候变化。北欧海洋和北极在过去十年中经历的显着变暖与 20 年代至 1930 年代的温暖时期相似。这两个时期的强度以及对北大西洋副极地和上覆大气的影响有多相似？在较短的十年时间尺度上，流入北欧海洋的大西洋水显示出巨大的变化，部分与气象学的大尺度模式有关。与此相关的是地表盐度异常，例如大盐度异常。这种变化的根源是什么，它与大气的关系，以及它的气候意义是什么？解决第二个目标将需要在大气/海洋/冰耦合模型中探索这些机制，特别是新的IPCC级模型运行，并使用同化研究的结果作为指导。耦合气候模型具有完整的物理特性，可以跟踪淡水和热量等属性在气候系统中的运动，同时与 SODA 和历史观测数据的比较提供了有关模型真实性的信息。更广泛的影响：该项目将通过开发和传播改进的 SODA 海洋再分析并提高对其不确定性的理解，为科学界提供对上层海洋温度、盐度和高纬度环流过去变化的改进分析。该项目参与北冰洋模式比对项目和其他场所将有助于促进对海洋再分析，特别是 SODA 的更多了解和使用。该研究项目的第二部分是提高对大洋盆地交换作用的理解，这是开发预测模型时需要了解的过程。该项目将包含大量的教育内容，将作为这项工作的一部分开发的数据集、分析和计算机资源免费提供给该系的研究生。

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.