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Isotopic evidence of multiple controls on atmospheric oxidants over climate transitions

机译：在气候变化中对大气氧化剂进行多重控制的同位素证据

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The abundance of tropospheric oxidants, such as ozone (O-3) and hydroxyl (OH) and peroxy radicals (HO2 + RO2), determines the lifetimes of reduced trace gases such as methane and the production of particulate matter important for climate and human health. The response of tropospheric oxidants to climate change is poorly constrained owing to large uncertainties in the degree to which processes that influence oxidants may change with climate(1) and owing to a lack of palaeo-records with which to constrain levels of atmospheric oxidants during past climate transitions(2). At present, it is thought that temperature-dependent emissions of tropospheric O-3 precursors and water vapour abundance determine the climate response of oxidants, resulting in lower tropospheric O-3 in cold climates while HOx (= OH + HO2 + RO2) remains relatively buffered(3). Here we report observations of oxygen-17 excess of nitrate (a proxy for the relative abundance of atmospheric O-3 and HOx) from a Greenland ice core over the most recent glacial-interglacial cycle and for two Dansgaard-Oeschger events. We find that tropospheric oxidants are sensitive to climate change with an increase in the O-3/HOx ratio in cold climates, the opposite of current expectations. We hypothesize that the observed increase in O-3/HOx in cold climates is driven by enhanced stratosphere-to-troposphere transport of O-3, and that reactive halogen chemistry is also enhanced in cold climates. Reactive halogens influence the oxidative capacity of the troposphere directly as oxidants themselves and indirectly(4) via their influence on O-3 and HOx. The strength of stratosphere-to-troposphere transport is largely controlled by the Brewer-Dobson circulation(5), which may be enhanced in colder climates owing to a stronger meridional gradient of sea surface temperatures(6), with implications for the response of tropospheric oxidants(7) and stratospheric thermal and mass balance(8). These two processes may represent important, yet relatively unexplored, climate feedback mechanisms during major climate transitions.
机译：对流层氧化剂的丰富性，例如臭氧（O-3）和羟基（OH）和过氧自由基（HO2 + RO2），决定了痕量气体（例如甲烷）的寿命以及对气候和人类健康至关重要的颗粒物的产生。对流层氧化剂对气候变化的响应受到的约束很有限，这是由于影响氧化剂的过程可能随气候变化的程度存在很大的不确定性（1），并且由于缺乏用于限制过去期间大气氧化剂水平的古记录气候转变（2）。目前，人们认为对流层O-3前体的温度依赖性排放和水蒸气的丰度决定了氧化剂的气候响应，导致在寒冷气候下对流层O-3较低，而HOx（= OH + HO2 + RO2）保持相对缓冲的（3）。在这里，我们报告了最近一次冰川-冰川间周期和两次Dansgaard-Oeschger事件中来自格陵兰冰芯的氧17-过量硝酸盐（代表大气中O-3和HOx的相对丰度）的观察结果。我们发现对流层氧化剂对气候变化敏感，因为在寒冷气候中O-3 / HOx比率增加，这与目前的预期相反。我们假设，在寒冷气候中观察到的O-3 / HOx的增加是由O-3在平流层至对流层中运输的增强驱动的，而在寒冷气候中，反应性卤素化学作用也得到增强。活性卤素直接作为氧化剂本身而影响对流层的氧化能力，并通过它们对O-3和HOx的影响间接影响（4）。平流层到对流层的传输强度主要由Brewer-Dobson环流控制（5），在较冷的气候中，由于海面温度的子午梯度更强（6）可能会增强，这对对流层的响应有影响氧化剂（7）和平流层热与质量平衡（8）。这两个过程可能代表了重要的气候过渡过程中重要的但尚未开发的气候反馈机制。

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  • 来源
    《Nature》 |2017年第7656期|133-136|共4页
  • 作者

    Geng Lei; Murray Lee T.; Mickley Loretta J.; Lin Pu; Fu Qiang; Schauer Andrew J.; Alexander Becky;

  • 作者单位

    Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA|Univ Grenoble Alpes, Inst Geosci & Environm, F-38508 Grenoble, France|Univ Sci & Technol China, Sch Earth & Space Sci, Hefei 230026, Anhui, Peoples R China;

    Univ Rochester, Dept Earth & Environm Sci, Rochester, NY USA;

    Harvard Univ, Sch Engn & Appl Sci, Cambridge, MA 02138 USA;

    Princeton Univ, Program Atmospher & Ocean Sci, Princeton, NJ 08544 USA;

    Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA;

    Univ Washington, Dept Earth & Space Sci, Seattle, WA 98195 USA;

    Univ Washington, Dept Atmospher Sci, Seattle, WA 98195 USA;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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