海洋混合过程对耦合模式气候敏感度影响

In the present climate models, under the fixed radiation forcing, the differences of simulated amplitudes of climate change are still large. This is due to large uncertainty in climate sensitivity. The climate sensitivity is close related to the oceanic heat uptake. The heat uptake is affected by ocean mixing processes. In the climate models, the mixing processes have large uncertainties. This will induce the large uncertainties in climate sensitivity. To understand the uncertainties in climate sensitivity due to ocean mixing processes, in the project, the relationships between ocean heat uptake and climate sensitivity are evaluated first based on the output from the 5th phase of Coupled Model Intercomparison Project. After evaluation, we will choose the key oceanic domains in which the oceanic heat uptake can greatly affect the climate sensitivity. Then we will carry on the experiments by adjusting the vertical and eddy-induced mixing processes in FGOALS models. We will distinguish the impact of oceanic mixing processes by comparing their simulations. Finally, the experiments are designed to identify the key oceanic domains in which oceanic mixing impacts the climate sensitivity. The project will help to reduce the climate sensitivity and reduce the uncertainty of prediction and projection of future climate if applied

在现有气候系统模式中，给定相同的辐射强迫，模拟的气候变化振幅仍有很大差异。这种差异是由于模式的气候敏感度不确定性造成的。气候敏感度不确定性与海洋热量吸收多少有关，而海洋吸收热量多少受海洋混合过程影响。在气候系统模式中， 海洋的混合过程存在较大的不确定性。这种不确定性会影响海洋热量分配和吸收，进而影响模式的气候敏感度。为了理解海洋混合过程不确定性对气候敏感度影响，本项目首先评估参加耦合模式比较计划第5阶段（CMIP5）模式模拟的海洋热量吸收与气候敏感度的关系，初步确定热量吸收对气候敏感度有重要作用的区域。接着采用FGOALS进行调整海洋垂直混合和涡旋混合过程数值耦合试验，并和未调整混合过程进行比对，确定海洋混合对海洋热量吸收和气候敏感度影响。最后，设计数值试验确认海洋混合对气候敏感度影响的关键区域。本研究顺利开展有利于减小模式的气候敏感度，同时也可减小对未来气候变化预估和预测的不确定性。

本项目利用CMIP5多模式模拟结果和一个耦合模式的数值试验，研究了气候敏感度的不确定性与海洋热吸收。通过分析气候敏感度、海洋热吸收与海洋过程之间的关系发现，海洋上层热吸收越大，气候敏感度越大，上层太平洋和印度洋的贡献不可忽视。对于深层，北大西洋、北冰洋和南大洋的海洋热吸收显著，这种作用与海洋环流关系紧密。大西洋经圈环流（AMOC）、热量吸收与气候敏感度关系密切，AMOC初始量值越大，气候敏感度越小，因为强的AMOC带更多热量进入海洋深层。潮汐和涡旋混合的主要影响区域主要位于大西洋和南大洋，通过环流影响热吸收。大西洋和南大洋的深层海洋热吸收对TCR具有重要贡献。本项目有利于减小海洋过程相关的气候敏感度不确定性。