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

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，该计划旨在启动全球定位系统(GPS)网络，以测量西南极冰盖(WAIS)周围和下面的基岩中的地壳运动。评估WAIS基岩的构造和冰致地壳运动的作用，对于理解WAIS过去、现在和未来的动力学及其在未来全球变化情景中的潜在作用，以及增进我们对南极洲在全球板块运动中的作用的理解，是一个至关重要的目标。南极洲西部的活动构造活动程度在很大程度上是推测的，因为几乎没有数据限制其地理分布、方向或变形速度。最近，地球物理数据表明，冰下火山活动和沉积盆地对冰流的控制，突显了活动构造作用和基岩对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根本性的问题。现有的全球定位系统项目仅位于冰盖边缘，不涉及区域情况。重要的是，必须开始在WAIS周围和内部的基岩上进行基线GPS测量，以便建立一个探测变化的基础。为了测量地壳运动，该项目将在2001-2002年南极野外考察季节开始的两年期间，在西南极(大约相当于从落基山脉到太平洋海岸的毗邻美国的大小)内部建立一个由至少15个GPS站点组成的西南极GPS网络(WAGN)。规划中的网络采用多模式占用战略(MOST)进行设计，即少数独立的全球定位系统“漫游”接收器与每个站点的连续全球定位系统站组成的网络进行相对较短时间的差分测量。这一试验性战略在加利福尼亚州、S美洲、西南部太平洋和中亚的一些项目中成功实施，最大限度地减少了后勤需求，这是全球定位系统大地测量在全球定位系统基岩零散和偏远露头中应用的基本要素。全球全球定位系统方案将与已建立的通过斯科舍弧连接南极半岛和南美洲的全球定位系统网络(Scotia Arc GPS Project，SCRAP)相结合。它还将与目前在罗斯湾测量运动的站点对接，并与南极研究科学委员会(SCAR)大地测量和地理信息系统工作组(SCAR)的全大陆巨型计划对接。GPS网络将建立在坚硬的岩石露头上的永久纪念碑上，这些纪念碑对漫游的GPS工作将具有接近零的设置误差，当未来的技术使整个南极洲的自主运行和卫星数据连接既可靠又经济时，这些纪念碑可以直接转换为连续的GPS站点。规划的网络既依赖于现有的和规划的连续网络，也是对现有网络和规划的连续网络的补充。目前，由于成本和后勤的原因，无论是通过连续站点网络还是传统活动来完成本文建议的测量都是不切实际的。拟议的WAGN将通过填补构成南极洲西部的几个离散地壳块之间的主要覆盖空白来补充现有的GPS项目，西南极洲是潜在基岩运动的关键区域。如果地壳运动相对缓慢，有意义的成果只有在个人资助项目的五年最长时间内才会开始显现。因此，这项提议只是为了启动网络，并在最关键的地点测试精度和速度。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，利率越慢，越早开始衡量就越重要。预计该项目的成果将启动一个迭代进程，逐步了解板块旋转以及冰川消融和冰块变化引起的粘弹性和弹性运动的贡献。从最关键位置的初始重新占用获得的速度将决定在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.