Abstract The ocean plays a crucial role in the global and regional climate. Many regional monsoon climates are interlinked by ocean currents and sea surface temperature (SST). The climate link between the East Asian and North American continent has been proposed and verified by many studies. A widely accepted hypothesis is that the precipitation of the monsoon marginal zone is strongly affected by the monsoon intensity. However, our rigorous test does not support a causal relation between precipitation in the monsoon marginal zone and summer monsoon intensity. Here we present systematic analysis with modern observation and simulation datasets, the Holocene paleoclimatic records and simulations from the East Asian summer monsoon (EASM) and North American summer monsoon (NASM) marginal zone to verify the relation between precipitation in the monsoon marginal zone and the ocean. Our results suggest that precipitation of the EASM and NASM marginal zone is affected by the Pacific SST and the El Nino-Southern Oscillation (ENSO) rather than the monsoon intensity. In particular, the impacts of SST lead to synchronous variations in the EASM and NASM marginal zone. With the global warming and increasing ENSO events, precipitation in the monsoon marginal zone, which locates in semi-arid regions, would reduce, resulting in an expansion of the semi-arid region.

中文翻译：

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东亚和北美夏季风边缘带降水在不同时间尺度上由热带太平洋海面温度引发的联系

摘要 海洋在全球和区域气候中起着至关重要的作用。许多区域性季风气候通过洋流和海面温度 (SST) 相互关联。许多研究已经提出并验证了东亚和北美大陆之间的气候联系。一个被广泛接受的假设是季风边缘带的降水受季风强度的强烈影响。然而，我们的严格测试并不支持季风边缘区降水与夏季风强度之间存在因果关系。在这里，我们使用现代观测和模拟数据集进行系统分析，东亚夏季风（EASM）和北美夏季风（NASM）边缘带的全新世古气候记录和模拟，以验证季风边缘带降水与海洋的关系。我们的研究结果表明，EASM 和 NASM 边缘带的降水受太平洋海温和厄尔尼诺-南方涛动 (ENSO) 的影响，而不是受季风强度的影响。特别是海温的影响导致 EASM 和 NASM 边缘区的同步变化。随着全球变暖和ENSO事件的增加，位于半干旱地区的季风边缘带降水将减少，导致半干旱地区的扩张。我们的研究结果表明，EASM 和 NASM 边缘带的降水受太平洋海温和厄尔尼诺-南方涛动 (ENSO) 的影响，而不是受季风强度的影响。特别是海温的影响导致 EASM 和 NASM 边缘区的同步变化。随着全球变暖和ENSO事件的增加，位于半干旱地区的季风边缘带降水将减少，导致半干旱地区的扩张。我们的研究结果表明，EASM 和 NASM 边缘带的降水受太平洋海温和厄尔尼诺-南方涛动 (ENSO) 的影响，而不是受季风强度的影响。特别是海温的影响导致 EASM 和 NASM 边缘区的同步变化。随着全球变暖和ENSO事件的增加，位于半干旱地区的季风边缘带降水将减少，导致半干旱地区的扩张。