Physical and Structural Properties of the Siple Dome Core

该奖项支持一项为期2年的更新计划，以继续研究Siple Dome冰芯的物理和结构特性。这项工作将包括继续监测岩芯松弛过程，进一步检查Siple Dome岩芯中保存的火山灰和尘埃记录及其与伯德岩芯中火山灰大面积降落的时间和分布模式的关系，以及可能的气候影响，从800米以下对冰进行额外的薄切片，以更准确地了解深层冰对变形增加和温度升高的反应，并测量底部含碎片冰中的总空气含量，以评估碎片在冰床中结合的机制。特别有趣的是正在进行的尝试，以解决气候记录在Siple圆顶和完善的时间尺度。目前，我们正在努力获得尽可能最好的深度年龄尺度，利用可视化地层学和ECM结合气体记录的年度层计数。最近提出的许多与气候有关的记录显示，在大约680米处可能有一个间断，在大约720米处可能有一个重大的气候事件。然而，在Siple圆顶核心层结构显示反向倾斜分层高达559米，并在更深的冰干扰和陡峭的倾斜分层的证据。关键是我们要确定这种结构扰动是否导致了气候记录的不连续性，或者是其他一些没有影响记录连续性的结构人为因素。除了对冰芯进行进一步的目视检查外，我们还计划在几个受干扰的冰结构区域制备垂直厚切片，以确定晶体结构是否显示出变形的证据。在这一过程完成之前，我们将无法知道地核有多深的地方存在着连续的气候记录。

This award supports a 2-year renewal program to continue research on the physical and structural properties of the Siple Dome ice core. This work will include continued monitoring of the core relaxation process, additional examination of the volcanic ash and dust record preserved in the Siple Dome core and its relationship to the timing and distribution pattern of widespread infall of tephra in the Byrd core, and possible climatic implications, additional thin sectioning of ice from below 800 m to obtain a more accurate picture of the response of the deeper ice to increased deformation and elevated temperatures, and measurements of total air content in the basal debris-bearing ice to evaluate mechanisms by which debris is incorporated at the bed. Especially intriguing are ongoing attempts to resolve the climate record at Siple Dome and to refine the time scale. Currently, we are working to obtain the best possible depth-age scale that utilizes annual layer counting based on visual stratigraphy and ECM in conjunction with the gas record. Many climate-related records from the Siple Dome core have recently been presented showing a possible hiatus at approximately 680 m and a potential major climatic event at around 720 m. However, the layer structure in the Siple Dome core shows reversed inclined layering as high as 559 m and evidence of disturbed and steeply inclined layering in deeper ice. It is critical that we determine whether this kind of structural disturbance has resulted in discontinuities in the climate record or is some other structural artifact that has not impacted the continuity of the record. In addition to conducting further visual examination of the core, we plan to prepare vertical thick sections in several regions of disturbed ice structure to determine if the crystal structure reveals evidence of deformation. Until this is complete, we will not know how deep into the core a continuous climate record exists.