Doctoral Dissertation Research: Holocene Fluctuations of Jakobshavn Ice Stream, West Greenland: Testing Climate Versus Topographic Controls on Ice Flow

更好地了解冰冻圈对气候变化的反应对于根据预计的世纪变暖准确估计海平面上升至关重要。最近，格陵兰冰盖的整体质量已经减少，部分原因是冰盖周边的冰流和出口冰川加速。然而，这些冰块的加速和短期波动使得预测未来冰盖退缩的速度和区域变化变得非常困难。此外，现代观测冰盖变化缺乏一个历史背景下，这些变化可以评估。 布法罗纽约州立大学的博士生尼古拉斯·杨将在杰森·布林纳博士的监督下重建格陵兰岛最大和最活跃的冰流雅各布港伊斯布雷尼亚过去的波动，并确定这些变化背后的驱动机制。 具体而言，本研究将探讨10，000年至8，000年前的冰缘进退是否受气候驱动，或者冰缘位置是否主要受非气候因素控制。 特别令人感兴趣的是测量9，200年至8，200年前发生的区域性百年尺度冷扰动是否引发了冰盖边缘的推进。 为了实现这些目标，这项研究将确定雅各布港Isbravn过去的范围使用铍同位素暴露测年的冰雕刻的基岩表面和巨石保存在景观的时间。 这项研究还将利用三维绘图技术来重建冰盖几何形状，这将有助于确定底层地形对冰盖波动的影响。 这项研究的更广泛的影响包括率先详细重建格陵兰岛一个主要冰流的短期古波动，评估雅各布港Isbravn对过去突发气候事件的敏感性，以及评估过去突发和短暂气候扰动期间雅各布港Isbravn行为的气候和冰动态控制之间的平衡。 这里使用的方法将有实际应用重建古冰缘变化的其他大型格陵兰冰流。 这一知识将导致开发模型，提高预测冰盖变化和由此产生的海平面变化的能力。

Improved understanding of the cryosphere's response to climate variability is essential for accurate sea-level rise estimates in light of projected 21st century warming. Recently, the overall mass of the Greenland Ice Sheet has decreased, driven in part by acceleration of ice streams and outlet glaciers located on the ice sheet periphery. However, acceleration and short-term fluctuations of these ice masses has made predicting the rate and regional variability of future ice sheet retreat extremely difficult. Furthermore, modern observations of ice sheet change lack a historical context against which these changes can be evaluated. Doctoral student Nicolás Young at the State University of New York Buffalo, under the supervision of Dr. Jason Briner will reconstruct past fluctuations of Jakobshavn Isbræ, Greenland's largest and most active ice stream, and determine the driving mechanisms behind these changes. Specifically, this research will explore if ice margin advance and retreat between 10,000 and 8,000 years ago was climate-driven, or if ice margin position was mainly controlled by non-climatic factors. Of particular interest is gauging whether regional, centennial-scale cold perturbations occurring between 9,200 and 8,200 years ago triggered an advance of the ice sheet margin. To achieve these objectives, this research will determine the timing of past extents of Jakobshavn Isbræ using beryllium-isotope exposure dating of ice-sculpted bedrock surfaces and boulders preserved on the landscape. This study will also utilize 3D mapping techniques to reconstruct ice sheet geometry that will assist in determining the influence of the underlying topography on ice sheet fluctuations. The broader impacts of this research include pioneering the detailed reconstruction of short-term paleo-fluctuations of a major ice stream in Greenland, assessing the sensitivity of Jakobshavn Isbræ to past abrupt climate events, and assessing the balance between climate and ice dynamic controls of Jakobshavn Isbræ behavior during past abrupt and short-lived climate perturbations. The methods used here will have practical applications for reconstructing paleo-ice margin changes of other large Greenland ice streams. This knowledge will result in the development of models that will improve the ability to predict changes in ice sheets and any resulting changes in sea-level.