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

该奖项支持一个项目，该项目将整合以前独立研究的三条冰川学研究线。首先，破冰雷达探测到的冰盖内层保留了过去冰积累时空格局的信息。冰流建模者可以利用地球物理反演方法恢复这些信息；然而，必须通过插值，在它们与一个年代确定的冰芯相交的地方知道这些层的年龄。其次，甲烷和其他一些大气成分的浓度随着气候的变化而随时间变化。然而，大气总是很好地混合在一起，并且在任何时候，世界范围内的浓度都是相似的，因此，来自一个未确定年代的核心的气体变化可以与GISP2这样一个确定年代的核心的气体变化相关联。因为近地表的空气很容易与上面的大气混合，所以被困在冰层深处气泡中的空气通常比冰层年轻数百到数千年。气体地球化学家必须用致密化模型计算出这种年龄差异，即三角洲年龄，然后才能准确地确定包围气体的冰层的年代。为了计算三角洲年龄，他们必须知道降雪时间和地点的温度和积雪率。第三，只有在大气变化的时候，才能将冰芯之间的气体联系起来，所以冰芯的日期必须在稀疏的日期点之间的深度进行插值。简单的插值方案会在深度-年龄剖面中产生不希望看到的伪影。这个项目的智力价值在于，它将开发新的插值方法来计算由于冰流力学而随时间变薄的冰层。准确的插值还需要一个时空积累历史。这三个问题通过积累模式和冰芯日期联系在一起。该项目将开发一个综合反演程序来同时解决这三个问题。新方法将结合破冰雷达剖面数据和冰芯数据，并将发现自洽的空间/时间积累模式；冰芯三角洲时代剖面；并且可靠地插值了深度-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；在钻探的初始阶段，利用从伯德站追踪到的估计年龄的雷达层，提供南极西部冰盖（WAIS）的初步深度年龄；并为南极洲Taylor Dome在过去20ka中建立了自洽的深度-年龄关系，在那里，低积累造成了测年、积累和三角洲年龄估计争议的不确定性。该项目更广泛的影响是，它将支持一名女研究生的博士研究，以及她在华盛顿大学妇女中心（University of Washington Women's Center）的非营利项目Making Connections中的持续推广工作。Making Connections旨在为专业女性导师和对数学和科学感兴趣的少数族裔高中女性配对，而这些学科传统上很少有女性参与。这名研究生还将参加为期十天的冰川实地项目“冰上女孩”（Girls on Ice），该项目由女性科学家导师授课，强调通过沉浸式科学观察、领导技能和安全意识。

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.