Forcings and Feedbacks: Arctic Sea Ice and the Atmosphere

强迫和反馈：北极海冰和大气

• 批准号: 0612779
• 负责人: Gudrun Magnusdottir
• 金额: $ 25.7万
• 依托单位: University of California-Irvine
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-08-01 至 2010-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0612779&HistoricalAwards=false
• 关键词: Forcings; Feedbacks; Arctic; Sea; Ice

Sea-ice concentration in the Arctic and the North-Atlantic part of the sub-Arctic has undergone pronounced trends in recent decades. Although driven in large part by changes in atmospheric flow, which had shown pronounced trends toward the positive phase of the North-Atlantic/Arctic Oscillation (NAO/AO) until the past couple of years, the trend in sea ice exerts a significant feedback upon the atmospheric circulation. In a preliminary modeling study the PIs found that the feedback due to sea-ice trends was strong, compared to that of sea surface temperature, and negative. This feedback was very sensitive to the location of the area of forcing, the most sensitive area being immediately east of Greenland and in the Barents Sea, areas that have highly variable sea-ice concentrations. The PI will carry out a more detailed evaluation of the nature of the subseasonal (monthly) feedback, especially late winter into spring and summer, including fractional sea ice area coverage, which was not represented in her preliminary study. The working hypothesis is that the atmospheric response to the forcing is still prominently projected onto the dominant climate pattern so that the response may be decomposed to first order into an "indirect" part, representing the projection onto the dominant pattern of atmospheric variability, and a "direct" part, representing the part of the response that is more local to the area of forcing. The PI will employ versions of the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM). The model will be forced with a 1% increase per year in atmospheric carbon dioxide (CO2) concentration and the effects of doubled and quadrupled atmospheric CO2 concentration on sea ice concentration patterns will be examined. Do the patterns resemble the patterns of the observed trend during different periods of the observational record over the past century? Even if they superficially resemble any of the observed trends, it will be interesting to apply this pattern of forcing (obtained from the forced coupled model) to the atmospheric general circulation model (AGCM), since the response is highly sensitive to small differences in the area of forcing at key locations. The motivation of the study is the need to detangle forcing/response due to natural/anthropogenic causes. The intellectual merit of the activity is that it seeks to understand and quantify the feedback of sea ice on the atmospheric circulation and its variability, which is poorly understood, while developing novel dynamical ideas regarding extratropical variability. The broader impacts of the activity are that it will improve our understanding of phenomena that are of fundamental interest in the Arctic climate system, indeed the entire climate system, while educating and training a PhD student, as well as undergraduate students.

近几十年来，北极和亚北极北大西洋部分的海冰浓度有明显的趋势。虽然在很大程度上是由大气流动的变化驱动的，直到过去几年，大气流动一直显示出北大西洋/北极涛动（NAO/AO）正相的明显趋势，但海冰的趋势对大气环流施加了重要的反馈。在初步的模拟研究中，pi发现，与海面温度的反馈相比，海冰趋势的反馈很强，而且是负的。这种反馈对强迫区域的位置非常敏感，最敏感的区域是格陵兰岛以东和巴伦支海，这些地区的海冰浓度变化很大。PI将对亚季节（每月）反馈的性质进行更详细的评估，特别是冬末到春夏的反馈，包括在她的初步研究中没有表现出来的海冰面积覆盖的分数。目前可行的假设是，大气对强迫的响应仍然突出地投射到主导气候型上，因此该响应可以分解为一级的“间接”部分（代表对大气变率主导型的投射）和“直接”部分（代表对强迫区域更局部的响应）。该项目将采用美国国家大气研究中心（NCAR）社区气候系统模型（CCSM）的版本。该模式将在大气二氧化碳浓度每年增加1%的情况下被迫运行，并将研究大气二氧化碳浓度增加一倍和四倍对海冰浓度模式的影响。这些模式是否与过去一个世纪观测记录中不同时期观测到的趋势模式相似？即使它们表面上与观测到的任何趋势相似，将这种强迫模式（从强迫耦合模式获得）应用于大气环流模式（AGCM）将是有趣的，因为响应对关键位置强迫面积的微小差异高度敏感。这项研究的动机是需要理清由于自然/人为原因造成的强迫/反应。这项活动的智力价值在于，它试图理解和量化海冰对大气环流及其变率的反馈，这一点目前知之甚少，同时发展出关于温带变率的新的动力学思想。这项活动的更广泛的影响是，它将提高我们对北极气候系统，实际上是整个气候系统中具有根本利益的现象的理解，同时教育和培训博士生和本科生。