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Inferring histories of accumulation rate, ice thickness, and ice flow from internal layers in glaciers and ice sheets.

机译：推断冰川和冰盖内层的累积速率，冰厚度和冰流量的历史记录。

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摘要

Spatial and temporal variations in past accumulation, ice thickness, and ice flow of polar ice sheets are weakly constrained on Earth, and are fundamental unknowns on Mars. On Earth, the spatial and temporal histories of accumulation and ice-sheet flow are necessary to recreate ice-volume and sea-level histories, and are important to properly interpret ice-core chemistry. On Mars, accumulation and ice-flow histories are necessary to decipher the connection between climate and ice-mass formation, evolution, and observable structure.;Internal layers in ice sheets on Earth and on Mars have been observed with ice-penetrating radar. These layers preserve information about how the ice sheet responded to past spatial and/or temporal changes in accumulation rate and ice flow, and present-day internal-layer shapes observed by radar are the most accessible remaining record of this past information. Deeper layers contain information from further in the past, making them highly valuable, but they are more difficult to decipher.;In this work, an inverse problem is solved to infer transients in accumulation rate, ice-sheet thickness, and ice flow from the shapes of deep internal layers. While some details of these histories can be recovered from ice cores, ice cores represent conditions at only a single point. However, the approach presented here is more robust in combination with ice-core data. If internal layers are dated, for example by an intersecting ice core, then radar-observed internal layers provide both spatial and temporal information. Each layer represents a past surface of a particular age that has been subsequently buried by accumulation and also modified by ice flow.;In this work, the goal of solving this inverse problem is to find a set of model parameters (e.g. accumulation-rate history) that have the minimum variation required to explain the data (e.g. internal-layer shapes). The process of internal-layer formation is described with a 2.5-D thermomechanical ice-flow flowband model. Estimates of the data are matched to measured values within their uncertainties, and to an expected tolerance. We seek an accumulation pattern that is spatially smooth, and a parameter set that is consistent with characteristic values of the parameters. This dissertation presents this inverse approach, and discusses applications to data from Antarctica and from Mars.
机译：过去积聚，冰层厚度和极地冰盖的冰流的时空变化在地球上受到了微弱的约束，这是火星上的基本未知数。在地球上，积累和冰盖流动的时空历史对于重建冰量和海平面历史是必不可少的，对于正确解释冰芯化学非常重要。在火星上，积累和冰流的历史对于破译气候与冰块的形成，演化和可观测结构之间的联系是必不可少的；穿透冰的雷达已经观测到了地球和火星上冰盖的内部层。这些层保留了有关冰盖如何响应过去的累积速率和冰流的空间和/或时间变化的信息，而雷达观测到的当今内层形状是该过去信息中最容易获得的记录。更深的层包含过去的信息，使其具有很高的价值，但更难于解密。在这项工作中，一个反问题得以解决，可以推断出积聚速率，冰盖厚度和冰流的瞬时变化。内部深层的形状。尽管可以从冰芯中恢复出这些历史的某些细节，但冰芯仅代表单个点的状况。但是，此处介绍的方法与冰芯数据结合使用时更加健壮。如果例如通过相交的冰芯确定了内部层的年代，则雷达观测到的内部层将同时提供空间和时间信息。每层代表特定年龄的过去表面，随后被堆积物掩埋，并被冰流改变。；在这项工作中，解决这一反问题的目的是找到一组模型参数（例如，堆积率历史） ）具有解释数据所需的最小变化（例如，内层形状）。用2.5维热机械冰流流带模型描述了内层形成过程。数据的估计值在不确定性范围内与测量值相匹配，并与预期的容差相匹配。我们寻求在空间上平滑的累积模式，以及与参数的特征值一致的参数集。本文提出了这种反演方法，并讨论了对南极和火星数据的应用。

著录项

  • 作者

    Koutnik, Michelle R.;

  • 作者单位

    University of Washington.;

  • 授予单位 University of Washington.;
  • 学科 Geophysics.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 294 p.
  • 总页数 294
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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