Collaborative Research: Paleoglaciology of Alaska -- Climate Parameters During the Last Glacial Maximum from GIS Determination of Equilibrium Line Altitudes

这是一个与来自科罗拉多大学和北方亚利桑那大学的主要研究者合作的项目。 更好地了解全球气候系统的最有效手段之一是了解最后一个冰河时代的条件，阿拉斯加是这种冰河时代实验的关键地区。 预计北极的环境响应将通过海冰范围、冰川/永久冻土融化、碳循环和冰的反馈来放大区域和全球气候变化。 阿拉斯加大部分地区在末次冰盛期（LGM）期间逃过了大陆冰川作用，这些地区的古气候代用指标是可用的。 评估陆地古环境对过去气候强迫的响应将使主要研究人员能够测试和改进全球和区域气候变化的环流模型，最近的进展使我们能够在区域尺度上以定量的空间方式从冰川地质记录中估计过去的气候参数，以便与气候模型进行直接比较。 山谷冰川是相对简单的气候记录器。 冬季降水和夏季气温局部控制的平衡线海拔（ELA）的垂直位置的个人冰川，积累和消融的总和等于零。 ELA的区域变化主要反映了冬季降水的空间变化。 阿拉斯加末次盛冰期期间冰川范围的气候动力学活动以前曾进行过定性评估，并表明阿拉斯加的降水量相对于目前已显着减少。 然而，没有人使用最近的经验回归降水和温度之间的ELA，也没有利用地理信息系统（GIS）进行空间计算，并产生过去的气候grids.The首席研究员建议使用冰川地质证据，进一步完善的记录，通过汇编末次冰期冰川在阿拉斯加的范围和生产的ELA变化和冬季降水异常的数字地图。 航空摄影和出版的地图将用于确定冰川轮廓。 对于选定的，研究不足的地区，他们建议进行实地研究，以限制LGM山谷冰川的限制，并评估其年龄。 这项工作将侧重于两个全州范围的横断面：一个从Kuskokwim山脉向西向东延伸到育空-塔纳纳高地，另一个从南向北沿着该州的西海岸延伸。 他们将使用碳14和宇宙成因同位素来确定LGM冰碛的绝对和相对年龄，如果有合适的岩石。 结合现代气候数据和末次盛冰期温度下降的估计，ELA可以用来计算末次盛冰期冬季降水。 全州范围的计算结果将与环流模式的输出结果进行比较，并为评估气候动态提供经验基础。 地理信息系统已经足够先进，我们现在可以把经验古气候数据的规模和全球环流模型的分辨率。

AbstractOPP-9977972OPP-9977974This is a collaborative project with Principal Investigators from the University of Colorado and Northern Arizona University. One of the most effective means for better understanding the global climate system is to understand the conditions during the last ice age and Alaska is a pivotal area for such ice-age experiments. Environmental response in the Arctic is expected to amplify regional and global climate change through feedbacks of sea-ice extent, glacier/permafrost melting, carbon cycling, and albedo. Paleoclimate proxies are available for large areas of Alaska that escaped continental glaciation during the Last Glacial Maximum (LGM). Assessing terrestrial paleoenvironmental response to past climate forcing will enable the Principal Investigators to test and refine global and regional circulation models of climate change.Recent advances enable us to estimate past climate parameters from glacial-geological records on a regional scale and in a quantitative, spatial manner for direct comparison with climate models. Valley glaciers are relatively simple recorders of climate. Winter precipitation and summer temperature locally control the vertical position of the Equilibrium Line Altitude (ELA) for individual glaciers, where the sum of accumulation and ablation equals zero. Regional variations in ELA's primarily reflect spatial variability in winter precipitation. Climate dynamic activities responsible for glacial extents during the LGM in Alaska have previously been assessed qualitatively and have suggested that Alaska has experienced a significant reduction in precipitation relative to the present. However, none have used recent empirical regressions between precipitation and temperature for ELAs, and none have taken advantage of the Geographic Information System (GIS) to perform spatial calculations and to produce past climate grids.The Principal Investigators propose to use glacial-geologic evidence to further refine the record by compiling LGM glacier extents in Alaska and produce digital maps of ELA variation and winter precipitation anomalies. Aerial photography and published maps will be used to determine glacier outlines. For selected, poorly studied areas, they propose to conduct field research to constrain the limits of LGM valley glaciers and to evaluate their age. This work will focus on two statewide transects: one spanning west to east from the Kuskokwim Mountains to the Yukon-Tanana Upland, and the other extending south to north along the western coast of the state. They will use carbon14 and cosmogenic isotopes to determine the absolute and relative ages of LGM moraines when suitable rocks available. In conjunction with modern climate data and estimates of LGM temperature depression, the ELA's can then be used to calculate LGM winter precipitation. The statewide computations will be compared with output from circulation models and will provide an empirical basis for evaluating climate dynamics. The GIS has advanced far enough to where we can now bring empirical paleoclimate data to the scale and resolution of global circulation models.