Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950
Eastward Shift of Interannual Climate Variability in the South Indian Ocean since 1950
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DOI：
10.1175/jcli-d-21-0356.1
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发表时间：
2021-10
影响因子：
4.9
通讯作者：
Lei Zhang;W. Han;K. Karnauskas;Yuanlong Li;T. Tozuka
中科院分区：
文献类型：
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作者：
Lei Zhang;W. Han;K. Karnauskas;Yuanlong Li;T. Tozuka
亚热带印度洋偶极子（SIOD）和宁加洛厄尔尼诺是南亚热带印度洋年际气候变化的两种主要模态。观测表明，近几十年来SIOD一直在减弱，而宁加洛厄尔尼诺一直在增强。在这项研究中，我们通过使用美国国家大气研究中心（NCAR）的地球系统模式第1版（CESM1）分析气候模式实验来探究这种变化的原因。CESM1大集合（CESM1 - LE）的集合平均结果表明，外部强迫对SIOD和宁加洛厄尔尼诺振幅的影响可忽略不计，这表明内部气候变化起主导作用。同时，CESM1起搏器实验的结果显示，这两种气候模态的观测变化不能归因于热带太平洋或热带印度洋的海表温度异常（SSTA）的影响。通过进一步比较CESM1 - LE的不同集合成员，我们发现一种年代际变化的暖池偶极子模态，其在印度洋东南部和热带太平洋中西部存在相反的SSTA，在驱动SIOD和宁加洛厄尔尼诺的观测变化中起着重要作用。这两种气候模态的这些变化对南印度洋区域的降水和海平面变化有相当大的影响。
The subtropical Indian Ocean Dipole (SIOD) and Ningaloo Niño are the two dominant modes of interannual climate variability in the subtropical South Indian Ocean. Observations show that the SIOD has been weakening in the recent decades, while Ningaloo Niño has been strengthening. In this study, we investigate the causes for such changes by analyzing climate model experiments using the NCAR Community Earth System Model version 1 (CESM1). Ensemble-mean results from CESM1 large-ensemble (CESM1-LE) suggest that the external forcing causes negligible changes in the amplitudes of the SIOD and Ningaloo Niño, suggesting a dominant role of internal climate variability. Meanwhile, results from CESM1 pacemaker experiments reveal that the observed changes in the two climate modes cannot be attributed to the effect of sea surface temperature anomalies (SSTA) in either the tropical Pacific or tropical Indian Oceans. By further comparing different ensemble members from the CESM1-LE, we find that a Warm Pool Dipole mode of decadal variability, with opposite SSTA in the southeast Indian Ocean and the western-central tropical Pacific Ocean plays an important role in driving the observed changes in the SIOD and Ningaloo Niño. These changes in the two climate modes have considerable impacts on precipitation and sea level variabilities in the South Indian Ocean region.