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The efficiency of baroclinic instability in the global ocean

全球海洋斜压不稳定的效率

基本信息

批准号：
2023590
负责人：
Stuart Bishop
金额：
$ 30.65万
依托单位：
North Carolina State University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2020
资助国家：
美国
起止时间：
2020-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2023590&HistoricalAwards=false
关键词：
efficiency baroclinic instability global ocean

项目摘要

This work will provide a better understanding of the pathways of energy in the global ocean and the exchanges with the atmosphere. These processes occur on different time and space scales and regulate Earth’s climate. The ocean generally gains energy (heat) in the tropics from the sun, which is then transported poleward by major ocean currents along the western boundaries of ocean basins, such as the Gulf Stream, and eventually lost back to the atmosphere in the midlatitudes. Recent research shows that oceanic turbulence in these midlatitude regions associated with strong current systems leads to a loss of energy to the atmosphere, not accounted for in traditional ocean circulation models. This sink of energy to the atmosphere at these turbulent time and space scales modulates the ocean circulation in unforeseen ways that need further investigation. This project will enhance our understanding of these processes and will develop parameterizations for their inclusion in general ocean circulation models leading to improving projections of Earth’s climate system. The study will combine remotely sensed data of sea surface height, surface temperature, and net heat flux collected over several decades with numerical simulations of coupled and uncoupled high-resolution Earth system models. The analysis will lead to better quantifying the rates and mechanisms of how energy is transferred from the ocean to the atmosphere and how this is associated with mesoscale eddies in the ocean. This proposal will support and help build the laboratory of an early career PI and the training of a PhD student. Public outreach lectures will be used to communicate the importance of the Gulf Stream in a changing climate.This work will aid in a better understanding of the pathways of energy in the global ocean. High-resolution climate models persistently have high sea surface temperature variance, but surface EKE comparable to observations. This proposal will help shed light on why this discrepancy occurs. Work in the Kuroshio Extension using a regional coupled model shows that this sink accounts for more than 70% of the EPE that would be available for conversion to eddy kinetic energy (EKE). However, it is still an open question how the OME-A sink connects to a modulation of EKE globally. This study will use multiple decades of available remote-sensed surface observations and a suite of global high-resolution simulations in coupled and uncoupled configurations of the Community Earth System Model (CESM-H) to access energy conversion rates through a local and global analysis. A local analysis requires a decomposition of the eddy heat flux field into divergent and rotational fluxes. The principal investigator will use Helmholtz decomposition to solve the Poisson equation globally in order to extract the dynamically important divergent fluxes. The main objectives are to 1) determine how the OME-A feedback modulates the efficiency of baroclinic instability to convert potential to kinetic energy in CESM-H; and 2) examine the spatial and temporal scale dependence of the EPE sources and sinks in state-of-the-art observations and CESM-H. There will be particular focus on the northern hemisphere Western Boundary Currents and their correspondence with decadal climate modes such as the North Atlantic Oscillation and Pacific Decadal Oscillation. A new parameter will be defined that does not depend on absolute model energetics and will allow model evaluations in current and future High-Resolution Model Intercomparison Projects such as the international Laboratory for High-Resolution Earth System Prediction (iHESP). The proposed team will collaborate with participants in the climate process team (CPT) on ocean transport and eddy energy and will ultimately contribute to a framework for parameterization development of the OME-A EPE sink in coarse-resolution coupled climate models.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

这项工作将使人们更好地了解全球海洋中的能量路径以及与大气的交换。这些过程发生在不同的时间和空间尺度上，并调节地球的气候。在热带地区，海洋通常从太阳获得能量（热量），然后通过主要洋流沿着海洋盆地的西部边界（如墨西哥湾流）向极地输送，最终在中纬度地区输回大气。最近的研究表明，在这些中纬度地区的海洋湍流与强大的电流系统导致能量损失到大气中，没有考虑到在传统的海洋环流模型。在这些动荡的时间和空间尺度上，能量向大气的下沉以不可预见的方式调节了海洋环流，需要进一步研究。该项目将加强我们对这些过程的了解，并将制定参数，以便将其纳入一般海洋环流模型，从而改进对地球气候系统的预测。这项研究将把几十年来收集的海面高度、表面温度和净热通量的联合收割机遥感数据与耦合和非耦合高分辨率地球系统模型的数值模拟结合起来。该分析将导致更好地量化能量如何从海洋转移到大气的速率和机制，以及这如何与海洋中尺度涡旋相关联。该提案将支持和帮助建立早期职业PI的实验室和博士生的培训。将利用公共外联讲座来宣传墨西哥湾流在气候变化中的重要性。这项工作将有助于更好地了解全球海洋中的能源路径。高分辨率的气候模式持续有高的海表温度的变化，但表面EKE观测。这一建议将有助于阐明为什么会出现这种差异。在黑潮延伸区使用区域耦合模式的工作表明，这个汇占70%以上的EPE，将可用于转换为涡动动能（EKE）。然而，它仍然是一个悬而未决的问题，如何OME-A汇连接到调制的EKE全球。这项研究将利用几十年的遥感地表观测资料和一套全球高分辨率模拟，在共同体地球系统模型（CESM-H）的耦合和非耦合配置中，通过当地和全球分析来评估能源转换率。局部分析需要将涡流热通量场分解为发散通量和旋转通量。主要研究者将使用亥姆霍兹分解来求解泊松方程，以提取动态重要的发散通量。主要目的是：1）确定OME-A反馈如何调节斜压不稳定性的效率，以将CESM-H中的位能转换为动能; 2）检查最新观测和CESM-H中EPE源和汇的时空尺度依赖性。将特别关注北方半球的西边界流及其与北大西洋涛动和太平洋十年涛动等十年气候模式的对应关系。将定义一个新的参数，它不依赖于绝对模式能量学，并将允许在当前和未来的高分辨率模式相互比较项目，如国际高分辨率地球系统预测实验室（iHESP）中进行模式评估。拟议的团队将与气候过程团队（CPT）的参与者合作，研究海洋运输和涡动能量，并最终为OME-A EPE汇在粗分辨率耦合气候模型中的参数化发展框架做出贡献。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估来支持。