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

Waddington/0636997该奖项支持一个项目，以整合三条线的冰川学研究，以前独立处理。首先，冰层的内部层，由冰层穿透雷达探测到，保留了过去冰积累的空间和时间模式的信息。冰流建模者可以使用地球物理逆方法恢复这些信息;但是，必须通过插值法知道这些层的年龄，因为它们与一个日期明确的冰芯相交。其次，甲烷和其他一些大气成分的浓度随着气候变化而变化。 然而，大气总是混合良好，并且在任何一个时间，全球范围内的浓度都是相似的，因此来自未注明日期的核心的气体变化可以与诸如GISP 2的日期明确的核心中的气体变化相关联。由于近地表的积雪中的空气很容易与上面的大气混合，因此被困在积雪深处气泡中的空气通常比积雪年轻数百到数千年。气体地球化学家必须计算出这种年龄差异，称为三角洲年龄，在封闭气体的冰可以准确地确定年代之前，使用积雪致密化模型。为了计算δ年龄，他们必须知道降雪时间和地点的温度和积雪速度。第三，只有在大气变化的时候，气体才能在冰芯之间相互关联，所以冰芯的日期必须在稀疏的日期点之间的深度内插。 简单的插值方案可能会在深度-年龄剖面中产生不期望的伪影。该项目的智力价值在于，它将开发新的插值方法，计算由于冰流力学而随时间变薄的层。准确的插值还需要空间和时间积累历史。 这三个问题是通过积累模式和冰芯日期耦合。 本项目将开发一个综合反演程序，同时解决所有三个问题。新方法将结合冰穿透雷达剖面数据和冰芯数据，并将找到自相一致的：空间/时间积累模式;冰芯的三角洲年龄剖面;以及可靠的内插深度年龄剖面。 然后，该项目将：在钻探的最初阶段，利用从伯德站追踪到的具有估计年龄的雷达层，提供南极西部冰盖的初步深度年龄;在过去的20 ka中，南极洲泰勒穹的深度-年龄关系是自洽的，那里的低积累造成了测年、积累以及对三角洲年龄估计的争议。 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，并支持她继续与“建立联系”开展外联工作，“建立联系”是华盛顿大学妇女中心的一个非营利方案，该方案将职业妇女导师与对数学和科学感兴趣的少数民族高中妇女配对，而在这些学科中，她们传统上代表性不足。研究生还将与冰上女孩合作，这是一个为期十天的冰川实地项目，由女科学家导师授课，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.