The numerical climate simulations from the Brazilian Earth System Model (BESM) are used here to investigate the response of the polar regions to a forced increase in CO₂ (Abrupt-4×CO₂) and compared with Coupled Model Intercomparison Project phase 5 (CMIP5) and 6 (CMIP6) simulations. The main objective here is to investigate the seasonality of the surface and vertical warming as well as the coupled processes underlying the polar amplification, such as changes in sea ice cover. Polar regions are described as the most climatically sensitive areas of the globe, with an enhanced warming occurring during the cold seasons. The asymmetry between the two poles is related to the thermal inertia and the coupled ocean–atmosphere processes involved. While at the northern high latitudes the amplified warming signal is associated with a positive snow– and sea ice–albedo feedback, for southern high latitudes the warming is related to a combination of ozone depletion and changes in the wind pattern. The numerical experiments conducted here demonstrated very clear evidence of seasonality in the polar amplification response as well as linkage with sea ice changes. In winter, for the northern high latitudes (southern high latitudes), the range of simulated polar warming varied from 10 to 39 K (−0.5 to 13 K). In summer, for northern high latitudes (southern high latitudes), the simulated warming varies from 0 to 23 K (0.5 to 14 K). The vertical profiles of air temperature indicated stronger warming at the surface, particularly for the Arctic region, suggesting that the albedo–sea ice feedback overlaps with the warming caused by meridional transport of heat in the atmosphere. The latitude of the maximum warming was inversely correlated with changes in the sea ice within the model's control run. Three climate models were identified as having high polar amplification for the Arctic cold season (DJF): IPSL-CM6A-LR (CMIP6), HadGEM2-ES (CMIP5) and CanESM5 (CMIP6). For the Antarctic, in the cold season (JJA), the climate models identified as having high polar amplification were IPSL-CM6A-LR (CMIP6), CanESM5(CMIP6) and FGOALS-s2 (CMIP5). The large decrease in sea ice concentration is more evident in models with great polar amplification and for the same range of latitude (75–90^∘ N). Also, we found, for models with enhanced warming, expressive changes in the sea ice annual amplitude with outstanding ice-free conditions from May to December (EC-Earth3-Veg) and June to December (HadGEM2-ES). We suggest that the large bias found among models can be related to the differences in each model to represent the feedback process and also as a consequence of each distinct sea ice initial condition. The polar amplification phenomenon has been observed previously and is expected to become stronger in the coming decades. The consequences for the atmospheric and ocean circulation are still subject to intense debate in the scientific community.

中文翻译：

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使用四倍量CO ₂实验的辐射强迫进行的半球间季节性极化比较

来自巴西地球系统模型（BESM）的数值气候模拟在此处用于研究极地地区对CO ₂强迫增加（突然4×CO ₂），并与耦合模型比较项目第5阶段（CMIP5）和第6阶段（CMIP6）仿真进行了比较。此处的主要目的是研究地表和垂直变暖的季节，以及极性放大背后的耦合过程，例如海冰覆盖率的变化。极地地区被描述为全球气候最敏感的地区，在寒冷季节，变暖现象加剧。两极之间的不对称性与热惯性和所涉及的海洋-大气耦合过程有关。在北部高纬度地区，放大的变暖信号与正的雪和海冰-反照率反馈相关，而对于南部高纬度地区，变暖与臭氧层消耗和风向变化的综合作用有关。此处进行的数值实验证明了极地扩增反应的季节性以及与海冰变化的联系的非常清楚的证据。在冬季，对于北部高纬度地区（南部高纬度地区），模拟的极地变暖范围从10到39 K（−0.5至13 K）。在夏季，对于北部高纬度地区（南部高纬度地区），模拟的变暖范围为0到23 K（0.5到14 K）。空气温度的垂直剖面表明，在地表，特别是在北极地区，变暖现象更强，这表明反照率-海冰的反馈与大气中经向热传递引起的变暖重叠。在模型的控制范围内，最大变暖的纬度与海冰的变化成反比。三种气候模式在北极寒冷季节（DJF）被确定为具有高极性放大作用：IPSL-CM6A-LR（CMIP6），HadGEM2-ES（CMIP5）和CanESM5（CMIP6）。对于南极而言，在寒冷季节（JJA），被确定为具有高极性放大作用的气候模型是IPSL-CM6A-LR（CMIP6），CanESM5（CMIP6）和FGOALS-s2（CMIP5）。^∘N  ）。此外，对于增暖的模型，我们发现5月至12月（EC-Earth3-Veg）和6月至12月（HadGEM2-ES）处于无冰状态的海冰年振幅具有表达变化。我们建议，模型之间发现的较大偏差可能与每个模型的差异有关，以代表反馈过程，也可能是每个不同海冰初始条件的结果。以前已经观察到了极性放大现象，并有望在未来几十年中变得更强。大气和海洋环流的后果仍需科学界激烈辩论。