Radar Systems for Glaciology
Radar Systems for Glaciology
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冰川学雷达系统
DOI：
10.5772/7179
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发表时间：
2010
影响因子：
3
通讯作者：
J. Baskaradas
中科院分区：
文献类型：
--
作者：
A. Zirizzotti;S. Urbini;L. Cafarella;J. Baskaradas
本章涉及雷达系统，测量和仪器，用于研究冰川学的内部核心和冰盖的基岩。地球的冰盖在格陵兰岛和南极洲。它们覆盖了地球陆地表面的10%。总积冰量占全球淡水储量的90%。这些与海洋环境有关的冰盖提供了一个重要的热汇，显著地调节了气候。冰川学研究的目的是了解流动（动力学），热力学和冰盖的长期行为所涉及的各种过程。对大冰块的研究是在不利的环境条件下进行的（极端寒冷，长时间的黑暗）。遥感技术的发展在取得有用成果方面发挥了重要作用。最广泛使用的技术是雷达系统，自20世纪50年代以来，为了满足提供快速和准确测量冰厚方法的需要，雷达系统被采用。由于全球变暖，极地研究年复一年变得越来越重要。此外，许多冰下湖泊区域（冰盖下截留的水）的发现引起了科学界对湖泊之间或冰下可能存在水循环的兴趣（Kapitsa等人，2006; Wingham等人，2006; Bell等人，2007年）。最近对雷达信号形状和振幅的研究可以提供冰下水循环的证据（Carter 2007，Oswald & Gogineni 2008）。在这一章中，雷达系统在冰川学，无线电回波探测（RES），简要介绍了一些有趣的结果。RES是利用穿透冰的电磁波的主动遥感系统。它们被用来获取不同界面（例如岩石-冰、冰-水、海水-冰）的电磁特性信息，这些界面将输入信号反射回雷达。RES系统的特点是高能量（峰值功率从10 W到10 KW）可变发射脉冲宽度（约从0.5 ns到几微秒），以便即使在冰盖最厚的区域（4755 m是使用RES系统在南极洲测量的最深冰厚）也能研究基岩特性。改变脉冲长度或发射信号频率，就有可能以不同的分辨率研究特定的冰盖细节。长脉冲允许传输比短脉冲更高的功率，穿透冰盖最厚的部分，但因此，分辨率降低。例如，地质雷达系统通常用于岩石、土壤、冰、淡水、路面和结构表征的地球物理学，它采用非常短的发射脉冲（0.5 ns至10 ns），可以详细描述冰盖的浅部（100-200 m深）（Reynolds 1997）。
This chapter deals with radar systems, measurements and instrumentation employed to study the internal core and bedrock of ice sheets in glaciology . The Earth's ice sheets are in Greenland and Antarctica. They cover about 10% of the land surface of the planet. The total accumulated ice comprises 90% of the global fresh water reserve. These ice sheets, associated with the ocean environment, provide a major heat sink which significantly modulates climate. Glaciology studies aim to understand the various process involved in the flow (dynamics), thermodynamics, and long-term behaviour of ice sheets. Studies of large ice masses are conducted in adverse environmental conditions (extreme cold, long periods of darkness). The development of remote sensing techniques have played an important role in obtaining useful results. The most widely used techniques are radar systems, employed since the 1950s in response to a need to provide a rapid and accurate method of measuring ice thickness. Year by year, polar research has become increasingly important because of global warming. Moreover, the discovery of numerous subglacial lake areas (water entrapped beneath the ice sheets) has attracted scientific interest in the possible existence of water circulation between lakes or beneath the ice (Kapitsa et al., 2006; Wingham et al., 2006; Bell et al., 2007). Recent studies in radar signal shape and amplitude could provide evidence of water circulation below the ice (Carter 2007, Oswald & Gogineni 2008). In this chapter the radar systems employed in glaciology, radio echo sounding (RES), are briefly described with some interesting results. RES are active remote sensing systems that utilize electromagnetic waves that penetrate the ice. They are used to obtain information about the electromagnetic properties of different interfaces (for example rock-ice, ice-water, seawater-ice) that reflect the incoming signal back to the radar. RES systems are characterized by a high energy (peak power from 10 W to 10 KW) variable transmitted pulse width (about from 0.5 ns to several microseconds) in order to investigate bedrock characteristics even in the thickest zones of the ice sheets (4755 m is the deepest ice thickness measured in Antarctica using a RES system). Changing the pulse length or the transmitted signal frequencies it is possible to investigate particular ice sheet details with different resolution. Long pulses allows transmission of higher power than short pulses, penetrating the thickest parts of the ice sheets but, as a consequence, resolution decreases. For example, the GPR system, commonly used in geophysics for rock, soil, ice, fresh water, pavement and structure characterization, employs a very short transmitted pulse (0.5 ns to 10 ns) that allow detailing of the shallow parts of an ice sheet (100-200 m in depth) (Reynolds 1997).