Self-consistent Ice Dynamics, Accumulation, Delta-age, and Interpolation of Sparse Age Data using an Inverse Approach

沃丁顿/0636997该奖项支持一个项目，该项目整合了之前独立处理的三条冰川学研究路线。首先，由穿透冰层的雷达探测到的冰盖内部层，保留了有关过去冰积累的空间和时间模式的信息。冰流模型建模者可以使用地球物理逆方法恢复这些信息；然而，必须通过插值法知道这些层的年龄，这些层与一个测年良好的冰芯相交。其次，随着气候的变化，甲烷和其他一些大气成分的浓度会随时间而变化。然而，大气总是很好地混合在一起，而且在任何时候全球范围内的浓度都是相似的，所以来自一个没有测年的岩心的气体变化可以与一个测年良好的岩心的气体变化相关联，比如GISP2。因为近地表积雪中的空气很容易与上面的大气混合，所以被困在积雪深处的气泡中的空气通常比积雪年轻数百到数千年。天然气地球化学家必须先用积雪致密模型计算出这一年龄差，然后才能准确测定包裹着天然气的冰层的年龄。要计算三角洲年龄，他们必须知道降雪的时间和地点的温度和积雪速率。第三，只有在大气变化的时候，才能在岩芯之间对比气体，所以冰芯的日期必须在稀疏的测年点之间的深度进行插补。过于简单化的内插方案可能会在深度-年龄分布中产生不需要的伪影。这个项目的智能优点是它将开发新的插值法，计算由于冰流力学而导致的随时间推移的地层变薄。准确的内插还需要空间和时间积累的历史。这三个问题通过堆积模式和冰芯日期联系在一起。该项目将开发一个综合的反演程序，以同时解决所有这三个问题。新方法将结合穿透冰层的雷达剖面数据和冰芯数据，并将找到自洽的：空间/时间堆积模式；冰芯的三角洲年龄剖面；以及可靠地内插的深度年龄剖面。然后，该项目将：重新计算南极洲伯德站的深度年龄剖面；使用从伯德站追踪的具有估计年龄的雷达层，在钻探的初始阶段提供西南极冰盖(WAIS)的初步深度年龄；并生成南极泰勒穹顶过去20ka的自洽深度年龄关系，那里的低积累在测年、积累和三角洲年龄估计方面造成了不确定性。该项目的更广泛影响是，它将支持一名女研究生的博士研究，以及她继续通过Making Connections进行的外展工作。Making Connections是一个非营利性项目，通过华盛顿大学女性中心，为专业女性导师与对数学和科学感兴趣的少数高中女性牵线搭桥，而她们在这些学科中的代表性传统上是不足的。这位研究生还将与冰上女孩合作，这是一个为期10天的冰川实地考察项目，由女科学家教师讲授，强调通过沉浸、领导技能和安全意识进行科学观察。

Waddington/0636997This award supports a project to integrate three lines of glaciology research, previously treated independently. First, internal layers in ice sheets, detected by ice-penetrating radar, retain information about past spatial and temporal patterns of ice accumulation. Ice-flow modelers can recover this information, using geophysical inverse methods; however, the ages of the layers must be known, through interpolation where they intersect a well-dated ice core. Second, concentrations of methane and some other atmospheric constituents vary through time as climate changes. However, the atmosphere is always well mixed, and concentrations are similar world-wide at any one time, so gas variations from an undated core can be correlated with those in a well-dated core such as GISP2. Because air in near-surface firn mixes readily with the atmosphere above, the air that is trapped in bubbles deep in the firn is typically hundreds to thousands of years younger than that firn. Gas geochemists must calculate this age difference, called delta-age, with a firn-densification model before the ice enclosing the gas can be dated accurately. To calculate delta-age, they must know the temperature and the snow accumulation rate at the time and place where the snow fell. Third, gases can be correlated between cores only at times when the atmosphere changed, so ice-core dates must be interpolated at depths between the sparse dated points. Simplistic interpolation schemes can create undesirable artifacts in the depth-age profile. The intellectual merit of this project is that it will develop new interpolation methods that calculate layer thinning over time due to ice-flow mechanics. Accurate interpolation also requires a spatial and temporal accumulation history. These three issues are coupled through accumulation patterns and ice-core dates. This project will develop an integrated inversion procedure to solve all three problems simultaneously. The new method will incorporate ice-penetrating radar profile data and ice-core data, and will find self-consistent: spatial/temporal accumulation patterns; delta-age profiles for ice cores; and reliably interpolated depth-age profiles. The project will then: recalculate the depth-age profile at Byrd Station, Antarctica; provide a preliminary depth-age at the West Antarctic Ice Sheet (WAIS) in the initial stages of drilling, using radar layers with estimated ages traced from Byrd Station; and generate a self-consistent depth-age relationship for Taylor Dome, Antarctica over the past 20ka, where low accumulation has created uncertainty in dating, accumulation, and controversy over delta-age estimates. The broader impacts of the project are that it will support the PhD research of a female graduate student, and her continued outreach work with Making Connections, a non-profit program through the University of Washington Women's Center, which matches professional women mentors with minority high-school women interested in mathematics and science, disciplines where they are traditionally under-represented. The graduate student will also work with Girls on Ice, a ten-day glacier field program, taught by women scientist instructors, emphasizing scientific observation through immersion, leadership skills and safety awareness.