Deciphering the Antarctic MSA-sea Ice Link with a Combined Regional Forecast and Atmospheric Chemistry Model

摘要PI：Cecilia M.Bitz Proposal Number：0739127标题：用区域预报和大气化学模式相结合的方法破译南极MSA-海冰联系智力优点：海冰在气候系统中发挥着多种重要作用，包括反射太阳辐射、影响海洋热吸收、促进稠水形成和通过抑制海浪作用保护冰架。南极海冰面积的可靠记录是自1979年以来才有的。为了进一步从数量上了解南极海冰在气候中的作用，对南极海冰状况进行长期记录将是非常可取的。海洋浮游植物产生二甲基硫化物(DMS)，排放到大气中，在那里可以被氧化成甲烷磺酸(MSA)和二氧化硫，最终沉积在大陆冰中。二氧化硫可以转化为非季节性(NSS)硫酸盐，也可以干燥地沉积到冰中。有人提出，沉积在冰芯中的MSA和NSS硫酸盐可以作为海冰状况的替代指标，尽管现有证据表明，这种关系可能会因几个因素而变得复杂，包括排放的可变性、运输的可变性、运输的反应和沉积的可变性。此外，海冰与排放之间的关系仍然存在不确定性。虽然人们可能认为海冰会限制浮游植物的生长，阻止DMS的逃逸，但在南极海冰融化的过程中，海洋环境中DMS的一些最高浓度已经被测量到。南极综合系统科学方案资助了这一项目，以使用跨学科建模方法来评估这些因素和不确定性，以帮助确定是否以及在哪里可以可靠地从南极冰芯冰芯中的MSA和NSS硫酸盐水平提取海冰条件。具体地说，将利用以社区多尺度空气质量(CMAQ)模拟系统为基础的相对较高分辨率的区域化学模式，审查1979-2002年期间MSA与气候的关系。气象条件将从极地MM5(俄亥俄州第五代宾夕法尼亚州立大学/国家大气研究中心中尺度模式的极地具体修改)的后预报输入/大尺度化学边界条件将从全球化学输送模式GEOS-Chem(戈达德地球观测系统-化学)输入。在与高纬度浮游植物和海冰藻类专家的合作安排下，将开发模型范围内海冰DMS排放的经验，并与包括海冰、浮游植物和海冰藻类的海洋大气环流模型的DMS排放进行比较。总的模型输出将与大气监测点的测量和冰雪沉积记录进行比较，包括作为国际极地年国际南极科学和教育穿越(ITASE)的一部分正在进行的广泛分布的年度分辨率记录。更广泛的影响：通过调查冰芯中MSA和NSS硫酸盐水平与海冰状况之间的联系，该项目可提供一个基础，帮助增进对南极海冰在全球气候系统中的作用的了解。该项目直接结合了全球气候建模、海冰和大气化学方面的专业知识，并通过合作，在海洋浮游植物生态方面。一名被认为是这项提议的构思的研究生将被支持在这个跨学科的主题上发表他的博士论文。作为海洋浮游植物生态合作的一部分，这名学生打算在澳大利亚与海洋冰藻二甲基磺酸丙酸酯(DMSP)生产专家一起参加NSF东亚太平洋夏季研究所的实习。与这项研究相关的推广活动将在西雅图太平洋科学中心举行的一年一度的极地科学周末上进行。其中两名研究人员是气候相关科学中代表性不足的群体(女性)的成员，并处于学术生涯的早期。

AbstractPI: Cecilia M. BitzProposal Number: 0739127 Title: Deciphering the Antarctic MSA-sea ice link with a combined regional forecast and atmospheric chemistry modelIntellectual merit: Sea ice plays multiple important roles in the climate system including reflecting solar radiation, influencing ocean heat uptake, contributing to dense water formation and protection of ice shelves by damping ocean wave action. Reliable records of Antarctic sea ice extent are only available since 1979. In order to further quantitative understanding of the role of Antarctic sea ice in climate, it would be highly desirable to have a longer term record of Antarctic sea ice conditions. Marine phytoplankton produce dimethylsulfide (DMS) which is emitted to the atmosphere where it can be oxidized to methanesulfonic acid (MSA) and sulfur dioxide and eventually deposited in continental ice. Sulfur dioxide can be converted to non seasalt (nss) sulfate or dry deposited to the ice. It has been suggested that MSA and nss sulfate deposited in ice cores can serve as a proxy for sea ice conditions although available evidence shows the relationship can be complicated by several factors including variability in emissions, variability in transport, reactions in transport and variability in deposition. Moreover there remain uncertainties with respect to the relationship between sea-ice and emissions. Whereas it might be presumed that sea ice would limit the growth of phytoplankton and prevent the escape of DMS, some of the highest concentrations of DMS in the marine environment have been measured in melting Antarctic sea ice. The Antarctic Integrated System Science Program ahs funded this project to use an interdisciplinary modeling approach to assess these factors and uncertainties to help determine whether and where sea ice conditions might be reliably extracted from MSA and nss sulfate levels in Antarctic ice cores ice cores. Specifically the MSA-climate relationship will be examined over the period of 1979-2002 using a relatively high resolution regional chemistry model based on the Community Multi-scale Air Quality (CMAQ) modeling system. Meteorological conditions will be input from hind-casts of Polar MM5 (Ohio State polar specific modifications of the fifth-generation Penn State University/National Center for Atmospheric Research Mesoscale Model)/ Large scale chemical boundary conditions will be input from a global chemical transport model, GEOS-Chem (Goddard Earth Observing System-Chemistry). Under collaborative arrangements with high latitude phytoplankton and sea ice algae experts, empirical DMS emissions within the model domain from sea ice will be developed and compared with modeled DMS emissions from an ocean general circulation model that includes sea ice, phytoplankton and sea ice algae. The overall model output will be compared with measurements from atmospheric monitoring sites and depositional records in snow and ice including widely distributed annually resolved records that are being undertaken as part of the International Polar Year (IPY) International Traverses of Antarctica for Science and Education (ITASE). Broader impacts: By investigating the links between MSA and nss sulfate levels in ice cores and sea ice conditions, this project could provide a basis to help advance the understanding of the role of Antarctic sea ice in the global climate system. The project directly combines expertise in global climate modeling, sea ice, and atmospheric chemistry and through collaboration, in marine phytoplankton ecology. A graduate student who is credited with conceiving of this proposal will be supported to conduct his PhD thesis on this interdisciplinary topic. As one element of the marine phytoplankton ecology collaboration, this student is intending to undertake an NSF East Asia Pacific Summer Institute internship in Australia with experts in sea ice algae dimethylsulfonic acid propionate (DMSP, a precursor to DMS) production. Outreach related to the research will be conducted at the annual Polar Science Weekend at the Pacific Science Center in Seattle. Two of the investigators are members of an underrepresented group (female) in climate related science and are early in their academic careers.