Collaborative Research: Did the Laurentine Ice Sheet Control Abrupt Climate Change?

这是与缅因大学和俄亥俄州立大学的合作项目。 首席研究员将模拟晚冰期劳伦泰冰盖，从距今 25,000 年前的近稳态平衡，通过与劳伦泰冰山爆发（海因里希事件 2 和 1）相关的可逆场间/场间转变，以及在距今 11,000 年前最后一次冰山爆发后跨越不可逆劳伦泰冰塌的阈值（海因里希事件 0）。 目标是确定冰盖变化是否可能通过冰盖突然变化引发气候变化，并调查这些变化的结构。 首席研究员将隔离冰盖数百年来突然变化的机制，这些机制大到足以引发气候变化，这些变化通过全球和区域大气气候模型的时间“快照”捕获。 具体的建模任务是：1）提供晚冰期期间劳伦泰德冰原周围“快照”的气候设置。 这包括冰盖上的风场、边界沿线的冰期湖泊、北美的高分辨率中尺度气候以及全球气候； 2) 提供基础边界条件，与内部流场和温度场一起用于计算基础质量平衡。 这包括基础温度、融化和冻结速率的模式，以及相关的冰下水文学； 3) 在选定时间范围内的强加边界和基础边界约束内对劳伦泰冰盖基础热、水文和机械条件进行建模； 4) 确定模型是否能够隔离允许劳伦太德冰快速前进和后退的突然变化机制，面积、海拔和体积的变化足以引发我们的区域和全球气候“快照”捕捉到的气候变化。该项目对于教育推广和当今冰盖的可能行为具有重要意义。 教育推广计划将与高中生互动。 他们将能够操纵主要变量，以便他们可以查看劳伦泰德冰盖如何响应每个变量的三维计算机模拟。 该计划将在万维网上传播。 如果劳伦泰德冰盖的波动引发了气候变化，那么目前覆盖格陵兰岛和南极洲的冰盖就有可能引发类似的气候变化，从而产生重大的社会、经济和政治后果。 评估这种可能性的一种方法是了解可能导致劳伦太德冰范围突然变化的内部不稳定机制，并将其与已知的晚冰期气候变化紧密联系起来。

This is a collaborative project with the University of Maine and Ohio State University. The Principal Investigators will model the late glacial Laurentide Ice Sheet from near steady-state equilibrium at - 25,000 BP (years before present), through reversible stadial/interstadial transitions associated with Laurentide iceberg outbursts (Heinrich events 2 and 1), and across the threshold of irreversible Laurentide collapse after the last iceberg outburst at - 1 1,000 BP (Heinrich event 0). The goals are to determine if ice-sheet changes could have triggered climate changes by abrupt ice sheet change and to investigate the structure of these changes. The Principal Investigators will isolate mechanisms of abrupt change over hundreds of years in the ice sheet that are large enough to trigger climate changes captured as time "snapshots" by coupled global and regional atmospheric climate models. Specific modeling tasks are: 1) to provide the climate settings surrounding the Laurentide Ice Sheet at "snapshots" of time during this late glacial period. This includes the wind field over the ice sheet, proglacial lakes along the border, the fine-resolution mesoscale climate of North America, and global climate; 2) to provide the basal boundary conditions that, together with the internal flow and temperature fields, are used to calculate the basal mass balance. This includes the pattern of basal temperatures, melting and freezing rates, and the associated subglacial hydrology; 3) to model the Laurentide Ice Sheet basal thermal, hydrological, and mechanical conditions within the imposed and basal boundary constraints for the chosen timeframe; and 4) to determine whether modeling will isolate mechanisms of abrupt change that allow rapid advance and retreat of Laurentide ice, with areal, elevation, and volume changes large enough to trigger climate changes that are captured by our "snapshots" of regional and global climate.This project has significance for educational outreach and the possible behavior of present-day ice sheets. The education outreach program will be interactive with high school students. They will be able to manipulate the major variables so that they can view three-dimensional computer simulations of how the Laurentide Ice Sheet responds to each variable. This program will be disseminated on the world-wide web. If fluctuations in the Laurentide Ice Sheet triggered climate changes, then the possibility exists that present-day ice sheets covering Greenland and Antarctica could trigger similar climate changes, with major social, economic, and political consequences. A way to assess this possibility is to understand the internal instability mechanisms that could have caused abrupt changes in Laurentide ice extent, and to tie them firmly to known late glacial climate changes.