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

0003619Dalziel 该奖项由极地项目办公室的南极地质和地球物理项目提供，支持启动全球定位系统（GPS）网络来测量西南极冰盖（WAIS）周围和下方基岩的地壳运动的合作研究项目。评估 WAIS 基岩的构造和冰引起的地壳运动的作用是了解 WAIS 过去、现在和未来的动态及其在未来全球变化情景中的潜在作用以及提高我们对南极洲在全球板块运动中的作用的理解的关键目标。西南极洲活跃构造活动的范围在很大程度上是推测性的，因为很少有数据可以限制其地理分布、方向或变形率。最近，地球物理数据强调了活跃的构造活动和基岩对 WAIS 的影响，这些数据表明活跃的冰下火山活动和沉积盆地的存在对冰流的控制。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 GPS 项目仅位于冰盖边缘，无法解决区域图景。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，以便为检测变化奠定基础。为了测量地壳运动，该项目将从南极野外季节开始的两年时间内，在整个西南极洲内部（大约相当于美国从落基山脉到太平洋海岸的面积）建立一个由至少 15 个 GPS 站点组成的西南极洲 GPS 网络 (WAGN) 2001-2002。规划的网络采用多模式占用策略（MOST）进行设计，其中少量独立的 GPS“流动”接收器在每个站点相对较短的时间内针对连续 GPS 站网络进行差分测量。 这一实验策略已在加利福尼亚州、南美、西南太平洋和中亚的多个项目中成功实施，最大限度地减少了后勤需求，这是在 WAIS 基岩分散且偏远的露头中应用 GPS 大地测量的基本要素。WAGN 计划将与已建立的通过斯科舍弧连接南极半岛与南美洲的 GPS 网络（斯科舍弧 GPS 项目 (SCARP)）集成。它还将与目前测量罗斯海湾运动的站以及南极研究科学委员会 (SCAR) 大地测量和地理信息系统工作组的全大陆 GIANT 计划连接。 GPS网络将基于设置在坚固岩石露头中的永久纪念碑，对于流动GPS作业来说，设置误差几乎为零，并且当未来的技术使整个西南极洲的自主操作和卫星数据链接既可靠又经济时，可以直接转换为连续的GPS站点。规划的网络既依赖又补充现有和规划的连续网络。由于成本和后勤方面的原因，通过连续站网络或传统活动来完成本文提出的测量是不切实际的。拟议的 WAGN 将通过填补构成西南极洲（潜在基岩运动的关键区域）的几个离散地壳块之间的覆盖范围的主要空白来补充现有的 GPS 项目。如果地壳运动相对缓慢，则只有在单个资助项目的五年最长期限内才会开始出现有意义的结果。因此，该建议只是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，网络将产生越来越有意义的结果。事实上，速度越慢，尽早开始衡量就越重要。预计该项目的结果将启动一个迭代过程，逐渐理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。从最关键站点的初始重新占领获得的速度将决定当发生可检测到的运动时重新占领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.