Collaborative Research: Arctic climate sensitivity to freshwater forcing: Improving model-data comparisons of the 8.2 ka event**

知识价值：主要研究人员将把气候模拟和古气候记录结合起来，以更好地了解北极气候系统对北大西洋淡水化的敏感性。模式预测的未来变化在大西洋纬向翻转环流（MOC）有一个大的传播值。由于MOC在确定环北大西洋气候方面起着核心作用，因此我们必须知道这些模型中的哪一个（如果有的话）具有预测MOC响应的技能。模式的一个有用的测试是模拟MOC过去的变化，当强迫和响应是合理众所周知的。一个时间段，8.2 ka的事件，已被选定为一个测试案例的几个建模组。在环北大西洋古气候记录中，这一事件被视为一个突然的冷却期。其假设的原因是冰川湖阿加西斯排水到哈德逊湾，和模拟完成的日期主要集中在这个强迫。然而，还有其他同时代的强迫，以及用于模拟淡水通量的方法的不确定性，尚待审查。PI将完成三组模拟，以量化这些额外强迫的重要性和强迫方法。这些模拟将使用NCAR社区气候系统模型第3版（CCSM 3）完成。第一组模拟的目标是比较不同的淡水添加方法，或“冲洗”方法。“没有公认的冲洗方法，他们的实验将使他们能够提出一个共同的方法建议。第二组模拟将系统地研究模型对除冰川湖排水外发生的其他三种淡水通量的响应。据推测，这些来源中的每一个都在产生海洋和气候反应方面发挥了特定的作用。在最后一组模拟中，他们将考虑额外的大气强迫的影响。这些额外的强迫以前没有在模型实验中考虑过，但可能对气候反应有贡献。这项研究将是在8.2 ka事件模拟中以现实的方式纳入所有重要作用力的第一步。这对于了解北极气候敏感性以及耦合气候模型准确反映这种敏感性的能力至关重要。更广泛的影响：大西洋MOC的变化可以在环北大西洋和更远的地方产生大而迅速的气候扰动。这项拟议中的研究将通过评估我们预测未来与北大西洋淡水增加相关的快速变化的能力来造福社会。主要研究人员将与NSF支持的其他研究人员以及参与Paleohosing模型相互比较项目的全球科学家进行协同合作。这项研究的成果将是他们生成的模型输出，并与古气候建模相互比较项目一起存档。模型数据也将通过NCAR CCSM古气候工作组提供给科学界。这项研究将增加代表性不足的群体的参与，包括女科学家和一名学生在NCAR的SOARS计划。

ABSTRACTMorrillOPP-0713951Otto-BliesnerOPP-0713971Intellectual merit: The Principal Investigators will integrate climate modeling and paleoclimate records to better understand the sensitivity of the Arctic climate system to freshening of the North Atlantic. Model projections of future changes in the Atlantic meridional overturning circulation (MOC) have a large spread of values. Because the MOC plays a central role in determining the climate of the circum-North Atlantic, it is essential that we know which, if any, of these models has skill in predicting the response of the MOC. One useful test of the models is to simulate past changes in the MOC, at times when the forcing and response are reasonably well known. One time period, the 8.2 ka event, has been selected as a test case by several modeling groups. This event is observed as an abrupt cool period in circum-North Atlantic paleoclimate records. Its hypothesized cause is the drainage of glacial Lake Agassiz into Hudson Bay, and simulations completed to-date have focused mainly on this forcing. There are, however, other coeval forcings, as well as uncertainties in the methods used to model freshwater fluxes, that have yet to be examined. The PIs will complete three sets of simulations to quantify the importance of these additional forcings and the forcing methodology. These simulations will be completed using the NCAR Community Climate System Model Version 3 (CCSM3). The goal of the first set of simulations will be to compare different methods of freshwater addition, or "hosing." There is no accepted method of hosing and their experiments will allow them to make recommendations for a common methodology. The second set of simulations will systematically investigate the model response to three other freshwater fluxes that occurred in addition to the glacial lake drainage. It is hypothesized that each of these sources played a particular role in generating the ocean and climate response. In the last set of simulations, they will consider the effects of additional atmospheric forcings. These additional forcings have not been previously considered in model experiments, but could have contributed to the climate response. The research will be a first step toward incorporating all significant forcings in a realistic manner in simulations of the 8.2 ka event. This is essential for understanding Arctic climate sensitivity and the ability of coupled climate models to accurately reflect this sensitivity. Broader impacts: Changes in the Atlantic MOC can produce large and rapid climaticperturbations in the circum-North Atlantic and beyond. The proposed research willbenefit society by evaluating our ability to predict future rapid changes associated with freshwater increases in the North Atlantic. The Principal Investigators will participate in synergistic collaborations with other researchers supported by NSF and with scientists worldwide participating in the Paleohosing Model Intercomparison Project. A deliverable of this research will be the model output they generate, archived with the Paleoclimate Modeling Intercomparison Project. The model data will also be available to thescientific community through the NCAR CCSM Paleoclimate Working Group. Thresearch will increase the participation of under-represented groups by including women scientist and a student in the SOARS program at NCAR.