Improving mass balance and glacier dynamics modeling on Arctic glaciers for better prediction and hindcasting

首席研究人员将利用阿拉斯加的麦考尔冰川作为主要野外考察地点，提高我们对多热陆地冰川物质平衡和冰川动力学的理解。具体地说，他们将试图更好地了解积雪内部积冰的过程，以更好地预测气候变化如何影响冰川动力学和体积变化。这项工作是在这个团队进行了五年的研究，并在麦考尔冰川长期研究项目中进行了50年的研究之后进行的。科学功绩。先前的研究表明，阿拉斯加北极冰川的表面物质平衡(SMB)越来越负，在过去的几年里，夏末的雪线上升到高于冰川海拔的水平。但传统的通过桩进行的SMB测量没有考虑到冰雪和裂缝内的融水重新冻结所造成的内部冰积累，近年来，由于没有表面积累，这将占到年积累的100%。阿拉斯加北极冰川的年平均气温约为零下10摄氏度，因此没有机会将多达一半的冬季积雪捕捉到地下，而不考虑这些积雪会阻碍我们理解和预测变化的能力。随着整个北极雪线的上升，随着以前干燥的积雪地区开始融化，内部积累的过程在全球变得越来越重要。首席调查员将通过深入的实地研究，提高根据天气条件进行内部积累的预测率。这些信息将被用来进一步改进霍克的质量平衡模型；然后，这些模型可以用来重建过去50年的完整质量平衡记录，使用区域气候模型作为输入，以过去15年的现场SMB和天气记录作为校准。这一累积记录将与使用50年地图比较计算的体积变化进行比较-使用为该项目制作的新地形图。然后，质量平衡的事后预测和预测将被用于驱动Pattyn的有限差分热机械流线模型。在之前对该模型的研究中，他们发现，如果气候保持不变，阿拉斯加北极地区的所有冰川将在几百年内消失。然而，通过与过去50年的速度和表面海拔时间序列进行比较，他们认为该模型的预测响应比实际慢，因为它对内部积累速度、冰温度和冰结构的约束很差。在这项研究的基础上，他们将构建1890年至2100年间美国北极地区几乎所有冰川的体积-面积比例时间序列。更广泛的影响：这项研究还将延长和改进麦考尔冰川现有的50年记录，作为美国北极唯一的此类记录，麦考尔冰川对冰川学具有内在价值。该项目将帮助支持至少两名研究生和一名博士后，并将产生一系列专业论文，以及流行的媒体文章和公开讲座，使用他们不断扩大的重复照片对集合，定性地记录北极的生态变化，以帮助解释我们研究的意义。

ABSTRACTNolanOPP-0714045The Principal Investigators will improve our understanding of the mass balance and ice dynamics of polythermal land-terminating glaciers using McCall Glacier in arctic Alaska as a primary field site. Specifically, they will try to better understand the processes of internal accumulation of ice within firn to better predict how climate change impacts glacier dynamics and volume change. This work follows five years of research by this team and 50 years of research within the long-term McCall Glacier research project. Scientific Merit. Prior research has shown that the surface mass balance (SMB) of arctic glaciers in Alaska is increasingly negative, with late-summer snow lines ascending higher than the glacier elevations in the last several years. But traditional SMB measurements via stakes do not account for internal accumulation of ice by refreezing of meltwater within firn and crevasses, which in recent years would account for 100% of the annual accumulation since there was no surface accumulation. With mean annual air temperatures of roughly -10 degrees C in Alaska's arctic glaciers, there is no opportunity to capture as much as half the winter snow pack within the subsurface, and not accounting for this mass hampers our ability understand and predict change. With snow lines rising throughout the Arctic, the processes of internal accumulation are becoming increasingly important globally as formerly dry firn areas begin melting. The Principal Investigators will improve prediction rates of internal accumulation from weather conditions through intensive field studies. This information will be used to further improve Hock's mass balance models; then these can be used to reconstruct a complete mass balance record for the past 50 years using regional climate models as input and the past 15 years of field SMB and weather records as calibration. This cumulative record will be compared with volume change calculated using a 50 year map-comparison using a new topographic map made for this project. Hindcasts and forecasts of mass balance will then be used to drive Pattyn's finite difference thermo-mechanical flow-line model. In previous work with this model, they found that if the climate remains unchanged, all the glaciers within arctic Alaska would disappear within a few hundred years. However, through comparisons with speed and surface elevation time-series of the past 50 years, they believe the model's predicted response is slower than actual, as it is poorly constrained for rates of internal accumulation, ice temperatures, and ice fabrics. Based on this research, they will construct a time-series of volume loss from 1890 to 2100 using volume-area scaling for nearly all of the glaciers in the geographically-defined US Arctic. Broader Impacts: This research will also extend and improve the existing 50-year record of McCall Glacier, which has intrinsic value to glaciology as the only such record in the US Arctic. This project will help support at least two graduate students and one post-doc, and will result in a series of professional papers, as well as popularpress articles and public lectures using their expanding collections of repeat-photo pairs that qualitatively document ecological change in the Arctic to help explain the significance of our research.