The Evaluation of Ocean Reanalyses in Their Determining Trends in Global Ocean Heat Content with a Novel Method

用新方法评估海洋再分析确定全球海洋热含量趋势的能力

• 批准号: 1736633
• 负责人: Xinfeng Liang
• 金额: $ 29.91万
• 依托单位: University of South Florida
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1736633&HistoricalAwards=false
• 关键词: Evaluation; Ocean; Reanalyses; Their; Determining

Detecting and understanding oceanic change and variability has become increasingly important, given the fact that they serve as major evidence for climate change as well as the need to interpret climate variability patterns such as the much-debated recent global surface warming slowdown. Central to this issue is the ability to reliably represent the ocean state globally and over its full depth. Many researchers have turned to describe and understand oceanic change and variability from ocean reanalyses (ORA), which are the combination of ocean models, atmospheric forcings, and ocean observations through various data assimilation methods and potentially provide more accurate information than observation-only or model-only based ocean estimations. Also, ORAs provide more variables and quantities to interpret and understand the oceanic change and variability. At present, estimates from ORAs, especially their temporal evolutions, are still sensitive to the change of the observing system, the errors of the dynamical model, atmospheric forcing, and the data assimilation methods. Many of the uncertainties are often flow dependent and are hard to identify and estimate. This research proposes a novel, yet simple way to discover the possible systematic errors and biases in the temperature estimates from ORAs and then utilizes the most physically consistent ORAs to perform analysis on the changes in global and regional OHC. The proposed study can potentially provide a unified view for the recently much-debated global surface warming hiatus, and will advance understanding of the decadal variability of ocean heat uptake as well as provide useful implications about the imbalance of radiation at the top of the atmosphere. The project will support an early career scientist and a graduate student contributing to building the next generation of scientists. In addition, it will contribute to the development of k-12 educational material explaining the role of the oceans in regulating climate change.In this project, a simple but rarely used method will be used to evaluate a large set of the existing ORA products and determine if they are suitable for examining climatic-scale changes in global and regional ocean heat content (OHC). This evaluation is based on examining the changes of the thermal-steric and halo-steric contributions to the global steric height over time. To first order, the size of the global halo-steric component should be very small, as it is controlled by changes in freshwater input into the global ocean. After evaluating existing ORAs, the ones selected as having the smallest potential errors in long-term OHC will be analyzed with a goal to better understand the processes that determine the observed OHC change and variability. The team will assess whether the decadal-scale slight reduction in surface temperature was real and whether it reflected transport of extra heat to deeper layers of the ocean. Researchers will also carry out the analyses with a focus to separate the contributions of isopycnal movement (heave) and change in water mass properties along isopycnals (spiciness). If available in the selected ORAs, the vertical heat flux and the associated dynamical variables will also be examined.

探测和了解海洋变化和变异性变得越来越重要，因为它们是气候变化的主要证据，也需要解释气候变异模式，例如最近备受争议的全球地表变暖放缓。这一问题的核心是能够可靠地代表全球海洋状态及其整个深度。许多研究人员已经转向描述和理解海洋变化和变率的海洋再分析（ORA），这是海洋模式，大气强迫和海洋观测的组合，通过各种数据同化方法，并可能提供更准确的信息比仅基于观测或仅基于模式的海洋估计。同时，奥拉斯提供了更多的变量和数量来解释和理解海洋的变化和变率。目前，奥拉斯的估计，特别是它们的时间演变，仍然对观测系统的变化，动力学模式的误差，大气强迫和资料同化方法敏感。许多不确定性通常与流量相关，难以识别和估计。本研究提出了一种新的，但简单的方法来发现可能的系统误差和偏差的温度估计从奥拉斯，然后利用物理上最一致的奥拉斯来执行全球和区域OHC的变化进行分析。拟议的研究可能为最近备受争议的全球表面变暖间断提供统一的观点，并将促进对海洋热量吸收的十年变化的理解，并提供有关大气顶部辐射不平衡的有用启示。该项目将支持一名早期职业科学家和一名研究生为培养下一代科学家做出贡献。此外，该项目还将协助编写解释海洋在调节气候变化中的作用的K-12教育材料，在该项目中，将使用一种简单但很少使用的方法来评估大量现有的ORA产品，并确定它们是否适用于研究全球和区域海洋热含量（OHC）的气候尺度变化。这种评估是基于检查随时间的变化的热位阻和卤位阻的贡献，全球立体高度。首先，全球卤位组成部分的大小应该是非常小的，因为它是由淡水输入到全球海洋的变化控制。在评价现有奥拉斯后，将对选择的在长期OHC中具有最小潜在误差的ORA进行分析，目的是更好地理解确定观察到的OHC变化和变异性的过程。该小组将评估十年尺度的表面温度轻微下降是否是真实的，以及它是否反映了额外的热量向海洋深层的传输。研究人员还将进行分析，重点是分离等密度线运动（起伏）和水体性质沿着等密度线变化（辛辣）的贡献。如果在选定的奥拉斯，垂直热通量和相关的动力学变量也将被检查。

项目成果

Vertical redistribution of salt and layered changes in global ocean salinity

• DOI: 10.1038/s41467-019-11436-x
• 发表时间: 2019-08
• 期刊: Nature Communications
• 影响因子: 16.6
• 作者: Chao Liu;Xin‐Zhong Liang;R. Ponte;N. Vinogradova;O. Wang