Southern Ocean surface temperatures and cloud biases in climate models connected to the representation of glacial deep ocean circulation
Southern Ocean surface temperatures and cloud biases in climate models connected to the representation of glacial deep ocean circulation
复制标题
与冰川深海环流表征相关的气候模型中的南大洋表面温度和云偏差
DOI：
10.1175/jcli-d-22-0221.1
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发表时间：
2023
影响因子：
4.9
通讯作者：
Suzuki Kentaroh
中科院分区：
文献类型：
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作者：
Sherriff-Tadano Sam;Abe-Ouchi Ayako;Yoshimori Masakazu;Ohgaito Rumi;Vadsaria Tristan;Chan Wing-Le;Hotta Haruka;Kikuchi Maki;Kodama Takanori;Oka Akira;Suzuki Kentaroh
用综合气候模式模拟和再现过去大西洋纬向翻转环流（AMOC）对了解过去气候变化以及检验模式模拟不同气候的能力是必不可少的。在末次盛冰期（LGM），与现代气候相比，重建显示AMOC变浅。然而，几乎所有最先进的气候模式都模拟了更深的LGM AMOC。结果表明，这种古资料-模式的差异部分与南大洋（70°-45 ° S）现代海表温度（SST）的气候模式偏差有关。从三个阶段的古气候模型相互比较项目的模型输出的分析表明，温暖的南大洋SST偏差的模型往往模拟加深的末次冰期AMOC，而相反的是观察到的模型与冷SST偏差。结果表明，SST偏差与末次大冰期AMOC深度异常之间存在0.41的正相关关系。使用敏感性实验与气候模型，我们表明，作为一个例子，在气候模型中的云热力学相的分数相关的参数的变化减少了偏暖SST在现代南大洋。模型的偏差较小的版本则在LGM处重现了较冷的南大洋，这增加了南极底层水的形成，并导致LGM AMOC变浅，而不会影响其他地区的LGM气候。结果突出了南大洋海面条件和云在模拟过去和未来全球气候中的重要性。然而，大多数模型模拟了一个更深的大西洋纬向翻转环流（AMOC）在末次冰期，这与古数据表明一个较浅的AMOC。在这里，使用多模型分析和敏感性实验与气候模型，我们表明，这种古数据模型的差异部分与现代南大洋的模型偏差。南大洋表面温度和云层的改善在末次盛冰期重现了南大洋的寒冷气候，由于南极底层水的形成增加，导致AMOC的强烈变浅。这些结果表明，在南大洋模拟过去的气候模式偏差的重要影响。
Simulating and reproducing the past Atlantic meridional overturning circulation (AMOC) with comprehensive climate models are essential to understanding past climate changes as well as to testing the ability of the models in simulating different climates. At the Last Glacial Maximum (LGM), reconstructions show a shoaling of the AMOC compared to modern climate. However, almost all state-of-the-art climate models simulate a deeper LGM AMOC. Here, it is shown that this paleodata–model discrepancy is partly related to the climate model biases in modern sea surface temperatures (SST) over the Southern Ocean (70°–45°S). Analysis of model outputs from three phases of the Paleoclimate Model Intercomparison Project shows that models with warm Southern Ocean SST biases tend to simulate a deepening of the LGM AMOC, while the opposite is observed in models with cold SST biases. As a result, a positive correlation of 0.41 is found between SST biases and LGM AMOC depth anomalies. Using sensitivity experiments with a climate model, we show, as an example, that changes in parameters associated with the fraction of cloud thermodynamic phase in a climate model reduce the biases in the warm SST over the modern Southern Ocean. The less biased versions of the model then reproduce a colder Southern Ocean at the LGM, which increases formation of Antarctic Bottom Water and causes shoaling of the LGM AMOC, without affecting the LGM climate in other regions. The results highlight the importance of sea surface conditions and clouds over the Southern Ocean in simulating past and future global climates.Significance StatementTo test the ability of comprehensive climate models, simulations of the Last Glacial Maximum (LGM) have been conducted. However, most models simulated a deeper Atlantic meridional overturning circulation (AMOC) in the LGM, which contradicts paleodata suggesting a shallower AMOC. Here, using multimodel analysis and sensitivity experiments with a climate model, we show that this paleodata–model discrepancy is partly related to model biases in the modern Southern Ocean. Improvements in Southern Ocean surface temperatures and clouds reproduce a colder climate over the Southern Ocean at the LGM, which causes an intense shoaling of the AMOC due to increased formation of Antarctic Bottom Water. These results demonstrate the important effect of model biases over the Southern Ocean on simulating past climates.