DIMETHYL SULFIDE CYCLING IN OPEN LEADS DURING THE ARCTIC OCEAN EXPEDITION 2001

全球气候与海冰变化、开放海洋生物地球化学循环和环流、大气辐射以及北冰洋上空的云层密切相关。相互作用的气-海-冰过程的不确定性导致不同的全球气候模型模拟的北极气候和全球气候之间的巨大差异。特别是，作为2001年第三次北极夏季考察的一部分，瑞典极地研究秘书处向研究界提供了一个独特的平台(IceBreaker Oden)，作为其2001年第三次夏季北极考察的一部分，必须在气候模式中更准确地反映北冰洋中新的气溶胶颗粒的形成和对大气的影响，以反映浮冰中的细长通道(几米宽和几公里长)对大气的影响。这项工作将使我们能够对气候和环境敏感地区从海冰/空气界面到云顶边界层的化学和相关过程进行协调研究。该国际计划被设计为一个综合方案，其中包括现场实验阶段和紧密耦合的建模工作。该计划的总体目标是确定和量化生物、化学、物理和气象过程的作用，这些过程控制着与北极地区辐射强迫和气候有关的气溶胶的形成、演变和性质。该国际计划的另一个目标是将结果纳入区域和全球气候模式，并提高计算气溶胶颗粒强迫气候的总体精度。选择北冰洋中部作为首选地点，试图提供更好的气溶胶对气候变化的作用信息，是基于其气候敏感性，因为其海冰在控制地面质量和能量通量方面的重要性，现有数据库相对稀少，以及跟踪整个气溶胶-云-辐射系统的可能性，而大陆或人为来源的干扰非常小。目前，人们非常关注冰盖变薄和扩展减少，也许会增加线索的产生。铅促进了热量和物质的交换，将大气与北冰洋联系在一起。这项提议的重点是夏季，此时融化最严重，铅最普遍。该项目将具体解决这样一个问题：“冰及其附近或下面的水柱中存在哪些生物来源的化合物，这些化合物可能参与产生空气中的颗粒物？”为此，该项目将量化开放铅表层海水中作为潜在气溶胶前体的二甲基硫、二甲基磺酸和S-氨基酸的丰度和产量，并确定开放铅的生物含量和水中的化学物质和颗粒(即POC、PON、POS、叶绿素a、微型浮游生物组成)。这些参数也将在适当和可能的情况下，在其他调查人员收集的冰和表面膜样本中进行测量。其他欧洲调查人员将解决海洋颗粒物及其衍生产品是如何进入空气中的问题，它们是否会导致大气中新的颗粒物形成或生长，以及在什么情况下。

Global climate is intimately connected to variability in sea ice, open ocean biogeochemical cycling and circulation, atmospheric radiation, and clouds over the Arctic Ocean. Uncertainty in the formulation of interactive air-sea-ice processes results in large differences between the arctic, and global, climates simulated by different global climate models. In particular, the effects of long, narrow channels (meters to hundreds of meters wide and kilometers long) in pack ice, also called leads, upon the atmosphere and the formation of new aerosol particles in the Arctic Ocean must be more accurately represented in climate models to allow possible feedbacks between them.The Swedish Polar Research Secretariat has presented the research community with a unique platform (Icebreaker Oden) as part of its third expedition to the summer Arctic in 2001 entitled "Sources of airborne particles over the remote Arctic Ocean and their climatic relevance". This effort will allow a concerted study of chemical and related processes from the sea-ice/air interface to the cloud-topped boundary layer in a climatically and environmentally sensitive region. The international program is designed as an integrated package, which includes both a field experimental phase and a closely coupled modeling effort. The overall aim of the program is to identify and quantify the role of the biological, chemical, physical and meteorological processes that control the formation, evolution, and properties of the aerosol relevant to radiative forcing and climate in the Arctic region. A further objective of the international program is to incorporate the results in both regional and global-climate models and to improve the overall accuracy in the calculation of climate forcing by aerosol particles.Selection of the central Arctic Ocean as the preferred site for an attempt to provide better information on the role of aerosols on climatic change is based on its climatic sensitivity given the importance of its sea ice in controlling mass and energy fluxes at the surface, the relatively sparse existing databases and the possibility of following the entire aerosol-cloud-radiation system with very little interference from continental or anthropogenic sources.Currently, a great deal of attention is being given to the thinning and decreased extension of pack ice, perhaps increasing the generation of leads. Leads facilitate the exchange of both heat and materials, coupling the atmosphere with the Arctic Ocean.The focus of this proposal is on the summer season when melt is maximal and leads are most prevalent . This project will specifically address the question of "What compounds of biological origin are present in the ice and in the water column next to or below it, and that may be involved in the production of airborne particles?" To this effect, the project will quantify the abundance and production of DMS, DMSP, and S-amino acids as potential aerosol precursors in surface seawater in open leads and also determine the biological content of the open leads and the chemicals and particles (i.e., POC, PON, POS, chlorophyll a, microplankton composition) in the water. These parameters will also be measured, when pertinent and possible, in ice and surface film samples collected by other investigators. Other European investigators will address issues concerning how the marine particles and derived products become airborne, whether they lead to new particle formation or growth in the atmosphere and under what circumstances.