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

合作研究：阿拉斯加古冰川学——根据 GIS 确定的末次盛冰期气候参数确定平衡线高度

• 批准号: 9977972
• 负责人: William Manley
• 金额: $ 38.11万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-11-01 至 2003-10-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9977972&HistoricalAwards=false
• 关键词: Collaborative; Research; Paleoglaciology; Alaska; Climate

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. TheGIS has advanced far enough to where we can now bring empirical paleoclimate data to the scale and resolution of global circulation models.

摘要OPP-9977972 OPP-9977974这是一个与科罗拉多大学和北亚利桑那大学的首席研究人员合作的项目。要更好地了解全球气候系统，最有效的方法之一是了解上一次冰河时期的条件，而阿拉斯加是此类冰河时期实验的关键地区。北极的环境响应预计将通过海冰面积、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。古气候指标适用于阿拉斯加在末次冰盛期(LGM)期间逃过大陆冰川作用的大片地区。评估过去气候强迫的陆地古环境响应将使首席研究人员能够测试和完善全球和区域气候变化的环流模式。最近的进展使我们能够从区域尺度上的冰川地质记录中估计过去的气候参数，并以定量的空间方式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。冬季降水和夏季温度局部控制着个别冰川的平衡线高度(ELA)的垂直位置，那里的积累和消融之和为零。ELA的区域变化主要反映了冬季降水的空间变异性。在阿拉斯加大冰川盛会期间，气候动态活动对冰川范围造成的影响此前已进行了定性评估，并表明阿拉斯加的降雨量较目前有了显着减少。然而，没有人使用最近降水和温度之间的经验回归来计算ELA，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。主要研究人员建议利用冰川地质证据，通过汇编阿拉斯加LGM冰川范围来进一步完善记录，并制作ELA变化和冬季降水异常的数字地图。将使用航空摄影和出版的地图来确定冰川轮廓。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山谷冰川的界限，并评估它们的年龄。这项工作将集中在全州范围内的两个横断面：一个横跨从西向东从库什科维姆山脉到育空-塔纳纳高地，另一个沿该州西海岸从南向北延伸。他们将使用碳14和宇宙成因同位素来确定冰川冰川的绝对和相对年龄，如果有合适的岩石的话。结合现代气候数据和对末次冰期降温的估计，ELA可以用来计算末次冰期冬季降水量。全州范围内的计算将与环流模型的输出进行比较，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足够的进步，我们现在可以将经验的古气候数据应用到全球环流模型的尺度和分辨率上。