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

这是一项与科罗拉多大学和北亚利桑那大学首席研究员的合作项目。更好地了解全球气候系统的最有效手段之一是了解上一个冰河时期的情况，而阿拉斯加是进行这种冰河时期实验的关键地区。预计北极的环境响应将通过海冰范围、冰川/永久冻土融化、碳循环和反照率的反馈放大区域和全球气候变化。对于末次盛冰期（LGM）期间没有大陆冰川作用的阿拉斯加大片地区，古气候代用物是可用的。评估陆地古环境对过去气候强迫的响应，将使首席研究员能够测试和改进气候变化的全球和区域环流模型。最近的进展使我们能够从区域尺度的冰川地质记录中以定量的、空间的方式估计过去的气候参数，以便与气候模式直接比较。山谷冰川是相对简单的气候记录者。冬季降水和夏季气温局部控制着单个冰川的平衡线海拔（ELA）垂直位置，在ELA上，冰川的累积和消融之和等于零。ELA的区域变化主要反映冬季降水的空间变异性。在阿拉斯加LGM期间负责冰川范围的气候动力活动先前已进行了定性评估，并表明阿拉斯加的降水相对于现在显着减少。然而，没有人使用最近的降水和温度之间的经验回归分析ELAs，也没有人利用地理信息系统（GIS）进行空间计算和生成过去的气候网格。首席研究人员建议利用冰川地质证据，通过汇编阿拉斯加的LGM冰川范围，进一步完善记录，并制作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的轮廓。对于选定的、研究较少的地区，他们建议进行实地研究，以限制LGM山谷冰川的极限，并评估它们的年龄。这项工作将集中在两个全州范围的横断面上：一个横跨从西到东的Kuskokwim山脉到育空-塔纳纳高地，另一个沿着该州的西海岸从南到北延伸。他们将使用碳14和宇宙成因同位素，在有合适岩石的情况下，确定LGM冰碛的绝对和相对年龄。结合现代气候数据和LGM温度下降的估计，ELA可以用来计算LGM冬季降水。全州范围内的计算将与环流模式的输出进行比较，并将为评估气候动力学提供经验基础。地理信息系统已经取得了长足的进步，我们现在可以将经验古气候数据转化为全球环流模型的尺度和分辨率。

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.