Dynamic Observations of the Evolution of Firn

利用现代光谱技术，PI将确定冰芯致密化和微观结构演变的机制作为深度的函数。 将在格陵兰的萨米特钻取一个80米长的雪芯，然后运到达特茅斯。 对于冰芯的浅部，那里的积雪受到季节性和昼夜温度梯度的影响，PI将在冰芯边界处施加格陵兰的原位温度梯度。 将使用连续的碳纤维增强CT来监测致密化和微观结构的演变。 对于地核的深部，在地核的整个长度上不存在格陵兰原位温度梯度。 然而，它确实经历了来自覆盖层重量的应力。 因此，PI将在深层岩心上进行格陵兰原位加载实验。 将使用连续的碳纤维增强CT来监测致密化和微观结构的演变。 在完成COMPCT实验后，将在配备冷台的扫描电子显微镜中对积雪进行切片和检查。 电子背散射和能量色散X射线光谱将用于确定冰晶的方向和局部微化学。专家组认为，为学生提供的专业发展途径，包括参加未来学院教学系列和为期10周的“传播科学”课程，构思得很好。 由于北极异常变暖，格陵兰冰盖正在迅速融化。 总的来说，冰盖储存的水足以使海平面上升6米。 冰盖融化的速度有多快仍然是一个悬而未决的问题。 控制冰盖融化的一个重要因素是它的物理特性。 在这项工作中，研究人员将从格陵兰的Summit Station提取80米的核心。 在达特茅斯的一个寒冷的房间里工作，研究人员将在岩心近地表部分的两端施加自然温度条件，并在岩心的较深部分施加压缩测试。 一套光谱技术将被用来监测三维实时致密化的核心和晶体取向的演变。 这些实验将提供模拟建模所需的众多物理参数的值，这些参数将用于确定未来几十年的熔化速率。

Using modern spectroscopy techniques, the PI will determine the mechanisms of ice core densification and microstructure evolution as a function of depth. An 80 meter firn core will be drilled at Summit, Greenland, and transported to Dartmouth. For the shallow part of the core, where the firn is subjected to seasonal and diurnal temperature gradients, the PI will impose Greenlandic in situ temperature gradients at the core boundaries. Continuous ìCT will be used to monitor densification and microstructure evolution. For the deep part of the core, where a Greenlandic in situ temperature gradient does not exist over the length of the core. However, it does experience stresses from the weight of the overburden. The PI will therefore conduct Greenlandic in situ loading experiments on the deep core. Continuous ìCT will be used to monitor densification and microstructure evolution. After the completion of the ìCT experiments, the firn will be sectioned and examined in a cold-stage-equipped scanning electron microscope. Electron backscattering and energy dispersive X-ray spectroscopy will be used to determine ice crystal orientations and local microchemistry.The panel thought that the path presented for the professional development of students, which include attending the Future Faculty Teaching series and the 10-week "Communicating Science" course, was well conceived. The Greenland ice sheet is rapidly melting due to extraordinary Arctic warming. All told, the ice sheet stores enough water to raise sea level by 6 meters. How fast the ice sheet will melt is still an open question. One important factor controlling the ice sheet melt is its physical properties. In this work, the investigators will extract an 80 meter core from the Summit Station, Greenland. Working in a cold room at Dartmouth the investigators will impose the natural temperature conditions on the two ends of the near surface part of the core and compression tests on the deeper part of the core. A suite of spectroscopy techniques will be used to monitor the 3-dimensional real-time densification of the core and the evolution of the crystal orientation. These experiments will provide the values of the numerous physical parameters required for simulation modeling, which will be used to determine the melt rates over the coming decades.