Isotopic signatures of stratospheric air at the Himalayas and beyond

同位素示踪喜马拉雅山脉的平流层气团入侵

Downward transport of stratospheric air significantly mnodifes the chemical and radiation budget of the Earth's atmosphere.The Tibetan Plateau including the Himalayas is the largest and highest plateau on Earth and one of the most climatically important,sen-sitive,and complex regions in the world.Its topography and ther-mal heating affect the evolution of the Asian monsoon system via its uplift,leading to complex stratospheric-tropospheric interac-tions that play an important role in the global mass budget[1].In addition,the plateau is impacted by both naturally and anthro-pogenically sourced chemicals and is the source area of many major Asian rivers providing a sustainable water supply and food security for billions of people[2].Constraining the intensity and integrated flux of stratosphere-to-troposphere transport and potential influences on atmospheric chemistry and deposition at the Tibetan Plateau and surrounding regions is therefore central to quantifcation of their consequences for the hydrosphere and cryosphere near term and in the future.

喜马拉雅山脉地区被认为是平流层气团入侵对流层的重要通道,但仍缺乏足够的观测证据评估平流层入侵过程的强度,及其对青藏高原和周边地区大气与表生环境的影响.本研究使用最新建立的高精度、高敏度宇生同位素硫35(平流层示踪物;半衰期约87日)分析技术,发现珠穆朗玛峰和处于其下风向的中国西南部的大气硫酸盐硫35浓度比其他中纬度地区要高,证明喜马拉雅山脉的平流层气团入侵事件在春季频繁发生,且其影响比我们之前所想要大.另外,本文也发现中国西南部硫酸盐气溶胶中的氧17异常(Δ17O:1.58‰~2.50‰)明显大于中国西部(1.00‰~1.59‰),且与硫35呈正相关关系,表明了硫酸盐Δ17O的变化与气团来源高度相关.硫酸盐Δ17O和其他半衰期较长的宇生同位素的长期变化若能被保存下来,将有机会为青藏高原古大气和古高度的重建提供全新的地球化学指标.