摘要:海洋在气候变暖过程中的重要性通常用海洋热吸收来衡量，热吸收的大小影响全球变暖的幅度。本文利用FGOALS-g2、FGOALS-s2（以下分别缩写为g2、s2）两个耦合模式的CO2浓度以每年1%速率增长（1pctCO2）试验，评估和分析海洋热吸收与气候敏感度的关系。结果表明：进入海洋净热通量（s2模式大于g2模式）会使得s2模式的海洋热吸收总体比g2模式大；更为重要的是，由于s2模式中的海洋热吸收主要集中在上层，使得耦合模式s2中的瞬态气候响应（TCR，或称气候敏感度）比g2大。当CO2浓度加倍时，在两个耦合模式中，海洋热吸收的空间分布呈现显著性的差异，s2模式中上层热吸收明显比深层大，上层热吸收主要位于太平洋和印度洋，而g2模式中上层和深层热吸收差别较小，深层主要位于大西洋和北冰洋。进一步研究表明，海洋热吸收分布特征与两个耦合模式海洋环流变化有关。在g2模式中北大西洋经圈翻转环流（AMOC）强度强且深度大，在CO2浓度加倍时，AMOC减弱小，这样AMOC可将热量带到海洋的深层，增加海洋深层热吸收。而在s2模式中，平均AMOC弱且浅，在CO2浓度加倍时，AMOC减弱明显，热量不易到达深层，主要集中在海洋上层，对气候敏感度影响更快且更强。海洋环流导致热吸收及其空间差异同时影响到气候敏感度的差异。因此，探讨海洋热吸收与气候敏感度之间的关系，利于明确气候敏感度不确定性的来源。
关键词:海洋热吸收/
气候敏感度/
经圈翻转环流
Abstract:OHU (Ocean Heat Uptake) can affect the magnitude of global warming rate and is an important way to measure global warming. By utilizing the experiments of 1% per year increase of CO2 concentration simulated by two coupled models FGOALS-g2 and FGOALS-s2 (hereafter abbreviated g2 and s2), this study assesses and analyses the relationship between OHU and climate sensitivity. The result shows that TCR (transient climate response, i.e., climate sensitivity) in s2 is larger than that in g2, which is mainly related to larger OHU accumulation in the upper ocean, as the larger net heat flux into the ocean in s2 (compared to g2) results in larger OHU as a whole in s2 than in g2. When CO2 is doubled, there are significant differences in spatial distribution of OHU in the two coupled models. The OHU in the upper ocean is significantly larger than that in the deep ocean in s2. In s2, the OHU in the upper ocean is mainly located in the Indian-Pacific Ocean. Different from s2, the OHU difference between the upper ocean and deep ocean is small in g2. The OHU in the deep ocean is mainly located in the Atlantic-Arctic Ocean. Furthermore, the OHU distribution is related to the change in the ocean meridional overturning circulation. The AMOC (Atlantic Meridional Overturning Circulation) in g2 is stronger and deeper than that in s2 in the piControl (Pre-industrial Control) experiment. Meanwhile, the change in the AMOC is relatively small when CO2 is doubled in g2. These changes can bring more heat into the deep ocean and result in increases of OHU in the deep ocean. The averaged AMOC in s2 is weak and shallow in the piControl experiment and weakens significantly when CO2 is doubled. The absorbed heat is retained mainly in the upper ocean, which exerts rapid and strong impacts on the climate sensitivity. Therefore, the OHU change and its spatial distribution induced by ocean circulation affect the climate sensitivity. For this reason, the study of the relationship between OHU and climate sensitivity can help clarifying the uncertainty sources of climate sensitivity.
Key words:Ocean heat uptake/
Climate sensitivity/
Meridional overturning circulation
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