SGER: Using CCSM4 to Study Greenland Ice Sheet Response to Anthropogenic Forcings

学术价值：格陵兰和南极冰盖对21世纪海平面上升的贡献是高度不确定的。最近政府间气候变化专门委员会(IPCC)第四次评估报告(AR4)中的大多数估计是使用相对粗糙的冰盖模式和全球气候模式(GCM)的输出强制获得的，不包括与冰盖变化相关的气候反馈。PI将通过使用与新版本的社区气候系统模式(CCSM4)双向耦合的动态冰盖模式来探索格陵兰冰盖对人为温室压力的响应。有了这种耦合，冰盖将能够通过改变表面反照率、地形和流入海洋的淡水通量来改变当地和全球的气候。当地气候的改变可能会改变冰盖物质平衡，需要加以考虑。这项研究将是第一次将美国大气-海洋GCM双向耦合到冰盖模式，其结果将构成CCSM对AR5海平面变化估计的主要贡献。PI和他的同事们将讨论以下研究问题：在各种强迫情景下，格陵兰冰盖表面融化和相关反馈的变化幅度；在类似的强迫情景中，快速流动特征，如出口冰川的演变；以及冰盖变化对当地和全球气候的潜在影响。气候变化预测将得到对以前间冰期的模拟的补充，当时海平面比现在高出3-6米。这项研究既紧迫又高风险。紧急，因为如果不能在2010年底之前完成并接受出版，这项研究将不会被考虑纳入IPCC关于全球气候变化的AR5。这是高风险的，因为冰盖过程既高度复杂，又在与气候过程不同的时间尺度上运行；这将是第一次尝试使用复杂的冰盖模型和最先进的地球系统模型之间的完全耦合的方法来模拟和预测冰盖和气候演变到人为作用力。更广泛的影响：这项研究将提供关于人为全球气候变化的影响和轨迹的宝贵见解，包括海平面变化的量化概率。它将为一位杰出的女性博士后科学家提供资金。

Intellectual Merit: The contribution from the Greenland and Antarctic ice sheets to 21st century sea level rise is highly uncertain. Most estimates in the recent Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4) were obtained using relatively crude ice sheet models forced with Global Climate Model (GCM) output, without including climate feedbacks associated with changing ice sheets. The PI will explore the response of the Greenland ice sheet to anthropogenic greenhouse forcing by using a dynamic ice sheet model bi-directionally coupled to the new version of the Community Climate System Model (CCSM4). With this coupling, ice sheets will be able to modify local and global climate via changes in surface albedo, topography, and freshwater fluxes to the ocean. Modifications of local climate could change the ice-sheet mass balance and need to be taken into account. This study will be the first with a U.S. Atmosphere-Ocean GCM coupled bi-directionally to an ice sheet model, and its outcomes will constitute a primary contribution of CCSM to AR5 estimates of sea level change. The PI and his colleagues will address the following research questions: the magnitude of changes in surface melting of the Greenland ice sheet and associated feedbacks, under a variety of forcing scenarios; the evolution of fast-flowing features, such as outlet glaciers, in similar forcing scenarios; and the potential impacts of ice sheet changes on local and global climate. Climate-change projections will be complemented by simulations of the previous interglacial, when sea level was 3-6 m higher than at present. This research is both urgent and high risk. Urgent, because if not completed and accepted for publication by late 2010 the research will not be considered for inclusion in the IPCC AR5 of global climate change. It is high risk because ice sheet processes are both highly complex and operate at different timescales than climate processes; this will be the first attempt to simulate and predict ice sheet and climate evolution to anthropogenic forcings using a fully coupled approach between a sophisticated ice sheet model and a state-of-the-art earth system model. Broader Impacts: The research will provide valuable insights about the impacts and trajectory of anthropogenic global climate change, including quantitative probabilities of sea level changes. It will provide funding for an outstanding female post-doctoral scientist.