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OUTCROP: New prOcess-based UndersTanding of ocean heat Uptake with an application to improved Climate pRojections for pOlicy and Planning

露头：基于新过程的海洋吸热理解，并应用于改进政策和规划的气候预测

基本信息

批准号：
NE/R010536/1
负责人：
Remi Tailleux
金额：
$ 43.48万
依托单位：
University of Reading
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2018
资助国家：
英国
起止时间：
2018 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FR010536%2F1
关键词：
OUTCROP New prOcess based UndersTanding

项目摘要

Future climate change projections provide essential guidance for the efforts to curb the global warming trend caused by human emissions of greenhouse gases. One of the most important factors controlling the rate of climate change is ocean heat uptake (OHU), which is responsible for limiting global warming by absorbing part of the excess radiative forcing due to greenhouse gases by the ocean. Unfortunately, the physical processes controlling OHU remain poorly constrained and understood, as they are all associated with small scale processes related to turbulent mixing of heat and salt, meso-scale ocean eddies, deep water formation, which we do not know how to represent accurately, as well as to the surface fluxes of heat and freshwater, which are difficult to observe and measure precisely. As a result, large uncertainties in climate projections remain that are directly attributable to our lack of precise knowledge about ocean heat uptake. To understand how to make progress, a firm theoretical understanding of the physics of vertical heat transfer associated with OHU appears to be essential. Unfortunately, the validity and usefulness of the standard vertical/advection diffusion model for the horizontally-averaged temperature, which has been the primary theoretical tool to think about the vertical heat transfer, has been repeatedly questioned over the years owing to its failure to account for such effects as a varying topography, isopycnal mixing and the existence of density-compensated temperature anomalies.To resolve the above difficulties, our group recently developed a new process-based vertical advection/diffusion model for the heat balance that exploits advances from the theory of ocean water masses accumulated over the past 50 years or so. The new model represents a considerable improvement over the previous one, in that it naturally explains the precise role of a varying topography, density-compensated temperature anomalies, isoneutral mixing, and differential surface heating on the vertical heat transfer, which had remained obscure in the standard model. In this proposal, our first objective will be to demonstrate the usefulness of this new process-based model to interpret and rationalise the simulated ocean heat uptake for a wide range of climate change scenarios including increasing CO2, stabilisation, radiative forcing overshoot, and a collapse of the Atlantic meridional overturning circulation. Our second objective will be to demonstrate that the major advances due to our new process-based understanding of ocean heat uptake can be translated into a major improvement in the accuracy of climate change projections using Simple Climate Models, with a particular application to the MAGICC model, and one developed by the Met Office Hadley Centre. Indeed, although the main physical basis for our current understanding of climate change relies on coupled atmosphere-ocean general circulation models (AOGCMs), these models are computationally very expensive to run. Therefore, simple climate models (SCMs) have been developed, which are able to mimic the climate response seen in the AOGCMs, but at a much reduced computational cost. SCMs represent a key tool in the study of climate change, and are being used for several purposes, e.g. simulating how the projections depend on key climate parameters, or for the interpretation of the AOGCM projections. SCMs are often used for policy advice and play a central role in the science forming the basis for Working groups 2 and 3 of the latest International Panel on Climate Change report, the main document at the origin of the recent Paris agreement aimed at limiting the overall global warming below 2C.The improved physical understanding of ocean heat uptake will significantly contribute to improved climate projections and reductions of associated uncertainties.

未来的气候变化预测为遏制人类排放温室气体造成的全球变暖趋势的努力提供了重要指导。控制气候变化速率的最重要因素之一是海洋热吸收（OHU），它通过吸收海洋温室气体造成的部分过量辐射强迫来限制全球变暖。不幸的是，控制OHU的物理过程仍然缺乏约束和理解，因为它们都与小尺度过程有关，这些过程与热和盐的湍流混合，中尺度海洋涡旋，深水形成有关，我们不知道如何准确地表示，以及热量和淡水的表面通量，难以精确观察和测量。因此，气候预测仍然存在很大的不确定性，这可直接归因于我们缺乏对海洋热量吸收的准确了解。为了理解如何取得进展，对与OHU相关的垂直传热物理学的坚定理论理解似乎是必不可少的。不幸的是，多年来，作为考虑垂直热传递的主要理论工具的水平平均温度的标准垂直/平流扩散模型的有效性和实用性一直受到质疑，因为它未能考虑诸如变化的地形、等密度混合和存在密度补偿温度异常等影响。我们的小组最近开发了一个新的基于过程的热平衡垂直平流/扩散模型，该模型利用了过去50年左右积累的海洋水团理论的进展。新的模型比以前的模型有了很大的改进，因为它自然地解释了变化的地形、密度补偿温度异常、等中性混合和差异表面加热对垂直热传递的精确作用，而这些在标准模型中仍然是模糊的。在这项提案中，我们的第一个目标将是证明这种新的基于过程的模型的有用性，以解释和合理化的模拟海洋热吸收的气候变化情景，包括增加二氧化碳，稳定，辐射强迫过冲，和崩溃的大西洋纬向翻转环流。我们的第二个目标将是证明，由于我们对海洋热吸收的新的基于过程的理解而取得的重大进展可以转化为使用简单气候模型对气候变化预测准确性的重大改进，特别是MAGICC模型，以及由气象局哈德利中心开发的模型。事实上，尽管我们目前对气候变化的理解的主要物理基础依赖于耦合大气-海洋环流模式（AOGCM），但这些模式的计算成本非常高。因此，简单的气候模式（SCM）已经开发出来，它能够模拟AOGCM中看到的气候响应，但计算成本大大降低。SCMS是气候变化研究中的关键工具，并用于多种目的，例如模拟预测如何取决于关键气候参数，或用于解释AOGCM预测。供应链机制经常用于政策咨询，并在构成国际气候变化专门委员会最新报告第2和第3工作组基础的科学中发挥核心作用，这是最近旨在将全球总体变暖限制在2摄氏度以下的巴黎协定的主要文件。不确定性