Collaborative Research: A GPS Network to Determine Crustal Motions in the Bedrock of the West Antarctic Ice Sheet: Phase I - Installation

0003619 Dalziel该奖项由极地计划办公室南极地质和地球物理计划提供，支持一项合作研究计划，启动全球定位系统（GPS）网络，以测量西南极冰盖（WAIS）周围和下面基岩中的地壳运动。对WAIS基岩的构造和冰致地壳运动的作用进行评估，是了解WAIS过去、现在和未来动态及其在未来全球变化情景中的潜在作用的关键目标，也是提高我们对南极洲在全球板块运动中作用的理解的关键目标。南极洲西部的活跃构造活动程度在很大程度上是推测性的，因为很少有数据能够限制其地理分布，方向或变形率。最近，地球物理数据显示活跃的冰下火山活动和沉积盆地对冰流的控制，突出了活跃的构造作用和基岩对WAIS的影响。基岩地壳运动对WAIS及其未来动力学的影响是一个基本问题。现有的全球定位系统项目仅位于冰盖的边缘，并不涉及区域情况。重要的是，必须开始对WAIS周围和内部的基岩进行基线GPS测量，以便为探测变化奠定基础。该项目将在整个西南极洲内陆建立一个至少有15个GPS站点的西南极洲GPS网络（WAGN）在2001-2002年南极考察季节开始的两年期间，计划中的网络是使用多模式占用战略设计的，其中少数独立的全球定位系统“巡回”接收器在每个站点相对较短的时间内对连续的全球定位系统台站网络进行差分测量。 这一实验性战略在加州、南美、西南太平洋和中亚的许多项目中得到成功实施，最大限度地减少了后勤需求，在WAIS基岩的分散和偏远露头中应用GPS大地测量的一个基本要素。WAGN计划将与通过斯科舍弧连接南极半岛和南美洲的GPS网络相结合（斯科舍弧形GPS项目（SCARP））。它还将与目前测量罗斯湾运动的台站以及南极研究科学委员会大地测量和地理信息系统工作组的全大陆GIANT方案进行对接。全球定位系统网络将建立在坚固的岩石露头上的永久性纪念碑上，这些纪念碑对于全球定位系统的巡回工作来说，设置误差几乎为零，而且当未来的技术使整个西南极洲的自动操作和卫星数据连接既可靠又经济时，可以直接转换为连续的全球定位系统站点。规划的网络既依赖于现有的和规划的连续网络，也是对现有的和规划的连续网络的补充。由于成本和后勤方面的原因，目前还不太可能用连续的台站网络或传统的活动来完成本文提出的测量。拟议的WAGN将填补构成南极洲西部的几个离散地壳块体之间的覆盖范围的一个主要空白，从而补充现有的GPS项目。南极洲西部是潜在基岩运动的关键区域。如果地壳运动相对缓慢，则只有在单个供资项目的最长五年期限内才能开始出现有意义的结果。因此，该建议仅用于启动网络，并在最关键的站点测试精度和速度。然而，一旦建成，随着时间的推移，该网络将产生越来越有意义的结果。事实上，利率越低，尽早开始测量就越重要。预计这一项目的结果将启动一个迭代过程，逐步解决冰川消退和冰量变化造成的板块旋转和粘弹性和弹性运动的贡献。从最关键站点的初始重新占用中获得的速度将决定当发生可检测到的运动时重新占用整个网络的后续建议的时间。

0003619DalzielThis award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a collaborative research program to initiate a Global Positioning System (GPS) network to measure crustal motions in the bedrock surrounding and underlying the West Antarctic Ice Sheet (WAIS). Evaluation of the role of both tectonic and ice-induced crustal motions of the WAIS bedrock is a critical goal for understanding past, present, and future dynamics of WAIS and its potential role in future global change scenarios, as well as improving our understanding of the role of Antarctica in global plate motions. The extent of active tectonism in West Antarctica is largely speculative, as few data exist that constrain its geographic distribution, directions, or rates of deformation. Active tectonism and the influence of bedrock on the WAIS have been highlighted recently by geophysical data indicating active subglacial volcanism and control of ice streaming by the presence of sedimentary basins. The influence of bedrock crustal motion on the WAIS and its future dynamics is a fundamental issue. Existing GPS projects are located only on the fringe of the ice sheet and do not address the regional picture. It is important that baseline GPS measurements on the bedrock around and within the WAIS be started so that a basis is established for detecting change.To measure crustal motions, this project will build a West Antarctica GPS Network (WAGN) of at least 15 GPS sites across the interior of West Antarctica (approximately the size of the contiguous United States from the Rocky Mountains to the Pacific coast) over a two-year period beginning in the Antarctic field season 2001-2002. The planned network is designed using the Multi-modal Occupation Strategy (MOST), in which a small number of independent GPS "roving" receivers make differential measurements against a network of continuous GPS stations for comparatively short periods at each site. This experimental strategy, successfully implemented by a number of projects in California, S America, the SW Pacific and Central Asia, minimizes logistical requirements, an essential element of application of GPS geodesy in the scattered and remote outcrops of the WAIS bedrock.The WAGN program will be integrated with the GPS network that has been established linking the Antarctic Peninsula with South America through the Scotia arc (Scotia Arc GPS Project (SCARP)). It will also interface with stations currently measuring motion across the Ross Embayment, and with the continent-wide GIANT program of the Working Group on Geodesy and Geographic Information Systems of the Scientific Committee on Antarctic Research (SCAR). The GPS network will be based on permanent monuments set in solid rock outcrops that will have near-zero set-up error for roving GPS occupations, and that can be directly converted to a continuous GPS site when future technology makes autonomous operation and satellite data linkage throughout West Antarctica both reliable and economical. The planned network both depends on and complements the existing and planned continuous networks. It is presently not practical, for reasons of cost and logistics, to accomplish the measurements proposed herein with either a network of continuous stations or traditional campaigns.The proposed WAGN will complement existing GPS projects by filling a major gap in coverage among several discrete crustal blocks that make up West Antarctica, a critical area of potential bedrock movements. If crustal motions are relatively slow, meaningful results will only begin to emerge within the five-year maximum period of time for an individual funded project. Hence this proposal is only to initiate the network and test precision and velocities at the most critical sites. Once built, however, the network will yield increasingly meaningful results with the passage of time. Indeed, the slower the rates turn out to be, the more important an early start to measuring. It is anticipated that the results of this project will initiate an iterative process that will gradually resolve into an understanding of the contributions from plate rotations and viscoelastic and elastic motions resulting from deglaciation and ice mass changes. Velocities obtained from initial reoccupation of the most critical sites will dictate the timing of a follow-up proposal for reoccupation of the entire network when detectable motions have occurred.