Oxidant production over Antarctica land and its export - OPALE

地球的大气层是一种氧化介质。南极洲高原正上方的大气被认为是一个纯净的环境，然而，最近发现南极大气的氧化能力非常高。来自积雪的氮氧化物（NO、NO2和HONO）和氧化化合物（如HCHO和H2O2）的排放被认为是罪魁祸首。化学排放主要由积雪中的光化学反应驱动，即阳光对积雪的作用驱动积雪中硝酸盐和过氧化氢的光解作用，产生积雪中氮氧化物的通量和积雪中的羟基自由基反应。雪是光化学反应的极好介质，因为相对于上面的大气，雪顶部10cm的光通量增强了。以前对这种雪大气化学的研究往往集中在大气测量和/或极地沿海地点。这项调查的目的之一是探索和解释南极洲高原大陆的高大气氧化能力，并将这种化学反应与南极沿海站的测量和大气化学/运输模拟研究联系起来。南极沿海站研究南极和沿海气团的混合物。这项研究将在位于南极高原的Dome C的重要的法国/意大利冰芯钻探地点进行。因此，这项工作的第二个目的是研究空气-雪化学对冰芯化学记录的影响，这些记录用于推断以前的气候。这项提议的研究新颖而出色，原因有三：1)国际团队正在研究积雪化学和大气化学。2)被困在南极冰芯中的硝酸盐等化学物质随深度的变化可能为过去的气候和气候变化事件提供最有力的证据，对这些证据的了解是准确预测未来气候变化所必需的。破译冰芯中存在的化学信号是一项重大挑战，因为各种过程可能导致初始沉积后化学物质从冰芯中流失。我们建议开发一种方法，通过在冰芯中记录的硝酸盐剖面可以用来获得过去大气中的氧化能力。3)圆顶C的冰雪没有季节性（没有夏季融化）。这将是第一次有机会在积雪中测量非季节性雪的光化学，这将不同于以往的所有工作。本提案请求NERC支持测量Dome C积雪的光学特性（反照率和光穿透深度），监测向下的大气辐射，建立光化学辐射传输模型，计算积雪中化学物质的光解速率和化学物质（NO, NO2， HONO等）的通量。这是国际运动的一个关键部分，英国南极调查局（BAS）的科学家测量了积雪中这些化学物质的通量，三组法国科学家测量了雪的微物理结构、大气中的氧化剂和雪中N和O的同位素值，并建立了大气模型，以探索空气从高原输送到沿海站时沿海站对内部氧化化学的反应。这项活动物超所值，因为法国极地计划IPEV提供付费物流。该提案允许英国科学家进入南极高原，而英国在那里没有科考站。这是一个绝佳的机会。项目合作伙伴都是世界顶尖的极地科学家。该活动是国际全球大气化学计划（IGAC）下的国际极地年活动，AICI（空气-冰化学相互作用）项目。

The atmosphere of the Earth is an oxidising medium. The atmosphere directly above the Antarctica plateau is thought to be a pristine clean environment, however the oxidising capacity of the Antarctic atmosphere has recently been found to be very high. Emission of nitrogen oxides (NO, NO2 and HONO) and oxidised compounds such as HCHO and H2O2 from the snowpack are thought to be responsible. The chemical emissions are mainly driven by photochemical reactions in the snow, i.e. the action of sunlight on snowpack drives photolysis of nitrate and hydrogen peroxide in the snow to produce fluxes of nitrogen oxides from the snowpack and hydroxyl radical reactions in the snowpack. Snow is an excellent medium for photochemical reactions owing to the enhancement in the light flux in the top 10cm of the snow relative to the atmosphere above. Previous studies of this snow-atmosphere chemistry have tended to concentrate on either atmospheric measurements and/or polar coastal sites. One aim of this investigation is to explore and explain the high atmospheric oxidising capacity over plateau continental Antarctica and link this chemistry with measurement and atmospheric chemistry/transport modelling studies with stations on costal Antarctica. Coastal Antarctic stations study a mixture of Antarctic and coastal air-masses. This study will be conducted at the important French/Italian ice-core drilling site at Dome C, located on the Antarctic plateau. Thus, the second aim of this work is to investigate the effect of air-snow chemistry on chemical records in ice cores used to infer previous climates. The proposed study is novel and excellent for three reasons: 1) The international team is investigating the snowpack chemistry AND the atmospheric chemistry. Many previous studies have tended to concentrate on the atmosphere, 2) The variation with depth of chemicals such as nitrate trapped in Antarctic ice cores potentially provides the strongest evidence available for past climate and climate change events, an understanding of which is required for the accurate predictions of future climate change. Deciphering the chemical signals present in the ice cores is a major challenge as various processes can lead to the loss of chemicals from the ice core after initial deposition. We propose to develop a method by which the nitrate profiles recorded in ice cores can be used to obtain oxidising capacity in past atmospheres. 3) The snow and ice at Dome C are not seasonal (no summer melting). This will be the first opportunity to measure photochemistry in snowpacks for non-seasonal snow and will be different to all previous work. The requested NERC support in this proposal is for the optical properties (albedo and light penetration depths of the Dome C snowpack to be measured, to monitor downwelling atmosphere radiation and the construction of a photochemical radiative transfer model to calculate photolysis rates of chemicals in the snowpack and fluxes of chemicals (NO, NO2, HONO etc) from the snowpack. This is a critical part of the international campaign which has British Antarctic survey (BAS) scientists measuring fluxes of these chemicals from the snowpack and three groups of French scientists measuring the snow microphysical structure, oxidants in the atmosphere and isotopic values of N and O in the snow and atmospheric modelling to explore the response of coastal stations to the interior oxidation chemistry as the air is transported away from the plateau to the coastal stations. The campaign is excellent value for money as the French Polar program IPEV is providing paid logistics. The proposal allows UK scientists access to the Antarctica Plateau, where the UK has no stations. This is a fantastic opportunity. The project partners are all world leading polar scientists. The campaign is an International Polar Year campaign under the International Global Atmospheric chemistry program (IGAC), AICI (air-ice chemical interactions) project.