Universidade de São Paulo, Instituto Oceanográfico, Praça do Oceanográfico, 191, Cidade Universitária, 05508-120 São Paulo, SP, Brazil.
Universidade de Brasília, Instituto de Geociências, Instituto Central de Ciências, Campus Darcy Ribeiro, 70297-400 Brasília, DF, Brazil.
An Acad Bras Cienc. 2022 Mar 25;94(suppl 1):e20210667. doi: 10.1590/0001-3765202220210667. eCollection 2022.
Polar regions are among the most affected areas by the current global warming. In the Southern Hemisphere (SH), impacts of a warmer climate include decrease in sea-ice extent, changes in oceanic and in atmospheric circulation. Recently, some of these impacts were reinforced by the positive phase of the Southern Annular Mode (SAM). SAM is the dominant mode of variability of the SH extratropical climate and manifests as a "ring-shape" regular pattern of atmospheric mean sea level pressure (MSLP) with opposite sign between mid and high SH latitudes. Over the last three decades, SAM has presented a positive trend, and some studies associate it to stratospheric ozone depletion and to an increase in greenhouse gases concentration. As this debate is still open, climate models constitute useful tools to understand the SH variability in future scenarios. Here we use monthly MSLP outputs from the Brazilian Earth System Model (BESM) to examine SAM temporal and spatial behavior in future climate scenarios compared to the historical period. Our results for the BESM simulations suggest that the mean spatial pattern of SAM does not change with global warming, but an increase in the radiative forcing may reinforce positive SAM values obtained for the historical period.
极地地区是当前全球变暖影响最严重的地区之一。在南半球（SH），气候变暖的影响包括海冰范围缩小、海洋和大气环流变化。最近，这些影响中的一些被南半球环状模（SAM）的正相位加强。SAM 是南半球中纬度气候的主要变化模式，表现为大气平均海平面气压（MSLP）的“环形”规则模式，中高纬度的大气平均海平面气压呈相反的符号。在过去的三十年中，SAM 呈现出正趋势，一些研究将其与平流层臭氧消耗和温室气体浓度增加联系起来。由于这场争论仍在进行中，气候模型是了解未来情景下南半球变化的有用工具。在这里，我们使用巴西地球系统模型（BESM）的每月 MSLP 输出，来研究未来气候情景下 SAM 的时间和空间行为，与历史时期进行比较。我们对 BESM 模拟的结果表明，SAM 的平均空间模式不会随全球变暖而改变，但辐射强迫的增加可能会加强历史时期获得的正 SAM 值。
