PNAS:变暖气候中的亚洲季风

摘要 : 中国科学院地质与地球物理研究所一项研究发现，东亚夏季季风带的历史趋势的指标提示，这个季风带可能由于气候变化而向北移动。

中国科学院地质与地球物理研究所一项研究发现，东亚夏季季风带的历史趋势的指标提示，这个季风带可能由于气候变化而向北移动。东亚夏季季风带在近几十年里正在向南迁移，伴随着中国北方的变干旱的趋势。为了研究这个季风带如何可能随着未来的气候变化而继续变动，Shiling Yang及其同事研究了在过去的气候变化时期里的季风带的变动，这些变动被保存在了黄土性土壤沉积物中的有机物中。这组作者测量了年代测定为末次盛冰期的大块有机物的碳同位素比率。同位素比率提供了对使用C4光合路径的植物的生物质的测量。C4植被的空间模式非常类似于现代季风降水模式，这提示古代植被模式可能表明了过去的季风位置。这组作者绘出了等值线标示的具有类似C4植物生物质的区域，结果发现了等值线标示10%到20%的C4生物质在末次盛冰期和温暖的全新世中期之间向西北迁移了大约300千米。这组作者说，这些结果提示，一个变暖的气候让季风带向北变动，而目前观测到的向南的趋势可能逆转并将降水带到中国北方。

原文链接：

Warming-induced northwestward migration of the East Asian monsoon rain belt from the Last Glacial Maximum to the mid-Holocene

原文摘要：

Glacial–interglacial changes in the distribution of C3/C4 vegetation on the Chinese Loess Plateau have been related to East Asian summer monsoon intensity and position, and could provide insights into future changes caused by global warming. Here, we present δ13C records of bulk organic matter since the Last Glacial Maximum (LGM) from 21 loess sections across the Loess Plateau. The δ13C values (range: –25‰ to –16‰) increased gradually both from the LGM to the mid-Holocene in each section and from northwest to southeast in each time interval. During the LGM, C4 biomass increased from <5% in the northwest to 10–20% in the southeast, while during the mid-Holocene C4 vegetation increased throughout the Plateau, with estimated biomass increasing from 10% to 20% in the northwest to >40% in the southeast. The spatial pattern of C4 biomass in both the LGM and the mid-Holocene closely reseMBLes that of modern warm-season precipitation, and thus can serve as a robust analog for the contemporary East Asian summer monsoon rain belt. Using the 10–20% isolines for C4 biomass in the cold LGM as a reference, we derived a minimum 300-km northwestward migration of the monsoon rain belt for the warm Holocene. Our results strongly support the prediction that Earth's thermal equator will move northward in a warmer world. The southward displacement of the monsoon rain belt and the drying trend observed during the last few decades in northern China will soon reverse as global warming continues.

doi: 10.1073/PNAS.1504688112

作者：Shiling Yang

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