Climatic Aspects of the Initiation of the Laurentide Ice Sheet.

626-在理解气候强迫机制和随后的大气环流模式方面取得了相当大的进展，这是在最后一次间冰期116,000年末启动Laurentide冰盖(LIS)所需的(KYR B.P.)然而，这些强迫机制的相对重要性及其与年际和更长时间尺度上的大气变化的关系尚未确定。首席调查员将利用最先进的高分辨率气候和冰盖模式，对加拿大东北部LIS的发起和开始进行全面和系统的模拟调查，以确定气候强迫的作用，它们对自然气候变异性的影响，以及模式分辨率对所获得结果的影响。目标和理由：首席研究人员将使用极地MM5区域气候模型和NCAR社区气候系统模型2(CCSM2)模拟当代和最后一次间冰期环境中的大气状态。CCSM2将产生全球尺度的大气、海洋、海冰覆盖和陆地表面的描述，而专门为高纬度开发的极地MM5将产生关于可能的LIS起始区的区域大气环流和地表特征的高分辨率描述。从以年际变化大为特征的当代环境中，他们将确定现代冰川起源的类似物，即在加拿大东北部产生异常冬季降水和凉爽夏季温度的独特大气环流模式。这些时期的数据将用于极地MM5对几种理想化的现代情景的模拟，以确定凉爽的夏季和潮湿的冬季在实现常年积雪方面的相对重要性。将使用适当的轨道、微量气体和植被边界条件，对116KYR B.P.的气候进行CCSM2/Polar MM5耦合模拟，以确定来自耦合气候模型的年际变化是否足以在适当的时间尺度和正确的位置实现冰川起始。来自极地MM5的快照输出将输入到高分辨率的三维冰盖缩小程序和冰盖模型中，用于数千年的冰盖模拟，以确定气候模型雪地是否足以发生冰川起始。模型冰盖的位置和时间将根据研究区域内观测到的冰川地质和地貌进行验证。在当代和上一次间冰期模型模拟结果的指导下，将进行具体的敏感性测试，以分离在116KYR B.P.发生冰川开始和开始的关键气候强迫机制。智力上的优点和更广泛的影响：该项目汇集了一支具有气象学、气候学、冰川学和冰川地质学专业知识的高素质科学家团队，以及复杂的数值模式，首次研究导致冰川开始的各种时间和空间尺度上发生的明确的大气过程。将气候的显式表示与高分辨率的冰盖模式相结合，将极大地促进我们对气候强迫变异性在末次间冰期和当前间冰期冰盖开始时的重要性的理解。由于自然变异性和人为强迫的相对作用对未来可能发生的气候变化非常重要，因此更好地了解最后一次间冰期-冰期过渡时的气候变异性将对未来气候情景中潜在的社会影响产生重要影响。将有丰富的材料可供在小学/中学、大学课堂和通过互动式因特网网站进行教育推广。两名博士生将通过这一研究项目接受培训，并将为市中心的高中青年提供暑期实习机会，以发展他们的科学技能。

626- Considerable advancements have been made toward understanding the climate forcing mechanisms and subsequent atmospheric circulation patterns that are required for the initiation of the Laurentide Ice Sheet (LIS) at the end of the last interglacial 116 thousand years (kyr B.P.) Yet, the relative importance of these forcing mechanisms, and their relationship to atmospheric variability on interannual and longer time scales, have not been determined. The Principal Investigators will undertake a comprehensive and systematic modeling investigation of the initiation and inception of the LIS over northeastern Canada, using state-of-the-art high-resolution climate and ice sheet models to determine the role of climate forcings, their influence on natural climate variability, and the impact of model resolution on the results obtained. Objectives and Justification: The Principal Investigators will model the atmospheric state in the contemporary and last interglacial environments using the Polar MM5 regional climate model and the NCAR Community Climate System Model 2 (CCSM2). CCSM2 will produce global-scale descriptions of the atmosphere, ocean, sea-ice cover, and land surface while Polar MM5, developed specifically for high-latitudes, will yield high-resolution descriptions of the regional atmospheric circulation and surface characteristics over the likely initiation region of the LIS. From the contemporary environment, which is characterized by large interannual variability, they will identify modern analogs for glacial initiation, that is, distinct modes of atmospheric circulation that yield exceptional winter precipitation and cool summer temperatures in northeastern Canada. Data from these periods will be used in Polar MM5 simulations of several idealized modern scenarios to determine the relative importance of cool summers versus wet winters in achieving perennial snow cover. Coupled CCSM2/Polar MM5 simulations of the climate at 116 kyr B.P. will be conducted, using appropriate orbital, trace gas, and vegetation boundary conditions, to determine whether the interannual variability from the coupled climate models is sufficient to achieve glacial initiation on appropriate time scales and in the correct locations. Snapshot output from the Polar MM5 will be input to a high-resolution, three-dimensional ice sheet downscaling routine and ice sheet model for multi-millennial ice sheet simulations to determine whether the climate model snowfields are sufficient for glacial inception to occur. The location and timing of the model ice sheet will bevalidated against observed glacial geology and geomorphology in the study region. Guided by the results from the contemporary and last interglacial model simulations, specific sensitivity tests will be conducted to isolate the critical climate forcing mechanisms for glacial initiation and inception to occur at 116 kyr B.P.Intellectual Merit and Broader Impacts: This project brings together a team of highly qualified scientists with expertise in meteorology, climate, glaciology, and glacial geology, along with sophisticated numerical models to address for the first time the explicit atmospheric processes occurring on various temporal and spatial scales that lead to glacial initiation. Coupling an explicit representation of climate to a high-resolution ice sheet model will greatly advance our understanding of the importance of climate forcing variability on ice sheet inception at both the last interglacial and the current interglacial. Because the relative roles of natural variability and anthropogenic forcing are of very important to possible future climate changes, a better understanding of climate variability at the last interglacial-glacial transition will have important implications for potential societal impacts in a future climate scenario. There will be abundant material available for educational outreach at elementary/ secondary schools, university classes, and through an interactive Internet web site. Two Ph.D. students will receive training through this research project and summer internships will be offered to inner city high school youth to develop their science skills.