Increased Amazon Basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability
Increased Amazon Basin wet-season precipitation and river discharge since the early 1990s driven by tropical Pacific variability
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DOI：
10.1088/1748-9326/abd587
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发表时间：
2021-02
影响因子：
6.7
通讯作者：
A. Friedman;M. Bollasina;G. Gastineau;M. Khodri
中科院分区：
文献类型：
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作者：
A. Friedman;M. Bollasina;G. Gastineau;M. Khodri
亚马逊流域是地球上最大的流域，从1990年代初到2010年代初，雨季降水量和旺季河流流量显著增加。一些研究将亚马逊流域水文循环的增加与太平洋信风增加、东太平洋海表温度（SST）冷却以及太平洋步行者环流的相关加强等十年趋势联系起来。然而，很难将太平洋十年变化的作用与同期温室气体和其他外部气候驱动因素的影响区分开来。在这里，我们分开的贡献，外部强迫太平洋年代际变化的气候模式实验相同的辐射强迫剂，但施加不同的热带太平洋风应力的比较两个大的合奏。一个集合约束热带太平洋风应力的长期气候学，抑制热带太平洋年代际变化;另一个集合施加观测到的热带太平洋风应力异常，模拟现实的热带太平洋年代际变化。比较亚马逊流域水文气候响应的两个合奏，使我们能够区分共同的外部强迫模拟太平洋信风变率的贡献。对于1992-2012年的趋势，观测到的热带太平洋风应力异常的实验模拟了太平洋和南美洲之间的步行者环流的加强以及太平洋-大西洋流域间SST对比的加剧，推动了亚马逊流域雨季降水和旺季流量的增加。相反，这些环流和水文加剧的趋势是不存在的气候热带太平洋风应力的模拟。这项工作强调了太平洋十年变化在推动水文循环变化和调节全球变暖对亚马逊流域水文气候影响方面的重要性。
The Amazon Basin, the largest watershed on Earth, experienced a significant increase in wet-season precipitation and high-season river discharge from the early 1990s to early 2010s. Some studies have linked the increased Amazon Basin hydrologic cycle to decadal trends of increased Pacific trade winds, eastern Pacific sea surface temperature (SST) cooling, and associated strengthening of the Pacific Walker circulation. However, it has been difficult to disentangle the role of Pacific decadal variability from the impacts of greenhouse gases and other external climate drivers over the same period. Here, we separate the contributions of external forcings from those of Pacific decadal variability by comparing two large ensembles of climate model experiments with identical radiative forcing agents but imposing different tropical Pacific wind stress. One ensemble constrains tropical Pacific wind stress to its long-term climatology, suppressing tropical Pacific decadal variability; the other ensemble imposes the observed tropical Pacific wind stress anomalies, simulating realistic tropical Pacific decadal variability. Comparing the Amazon Basin hydroclimate response in the two ensembles allows us to distinguish the contributions of external forcings common to both simulations from those related to Pacific trade wind variability. For the 1992–2012 trend, the experiments with observed tropical Pacific wind stress anomalies simulate strengthening of the Walker circulation between the Pacific and South America and sharpening of the Pacific–Atlantic interbasin SST contrast, driving increased Amazon Basin wet-season precipitation and high-season discharge. In contrast, these circulation and hydrologic intensification trends are absent in the simulations with climatological tropical Pacific wind stress. This work underscores the importance of Pacific decadal variability in driving hydrological cycle changes and modulating the hydroclimate impacts of global warming over the Amazon Basin.