Radar Systems for Glaciology

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 and 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). Consequently, in recent years, GPR systems are also employed by explorers to find hidden crevasses on glaciers for safety. RES surveys have been widely employed in Antarctic ice sheet exploration and they are still an indispensable tool for mapping bedrock morphologies and properties of the last unexplored continent on Earth. The advantage of using these remote sensing techniques is that they allow large areas to be covered, in good detail and in short times using platforms like aeroplanes and surface vehicles

Twenty years of geomagnetic field observations at Mario Zucchelli Station (Antarctica)

During the 1986-87 austral summer a geomagnetic observatory was installed at Terra Nova Bay. During the firstyears both geomagnetic field time variation monitoring and absolute measurements were carried out only duringsummer. Since 1991 variometer measurements are automatically performed throughout the year, while absolutemeasurements are still performed only during summer. In spite of this, interesting observations were obtainedduring the life (quite long for Antarctica) of the geomagnetic observatory. In particular, this paper brieflypresents some of the most important results: studies on secular variation, daily variation (and its dependencefrom solar cycle and seasons) and geomagnetic higher frequency variations, such as geomagnetic pulsations

Ground magnetometric surveys end integrated geophysical methods for solid buried waste detection: a case study

The detection of illegal buried waste by means of geophysical techniques has recently become a major effort in shallow geophysical investigations. In particular, detection and location of underground metallic storage tanks can be accomplished using different instruments and techniques. In this paper we describe the results of an investigation carried out in a tuff quarry in Riano Flaminio (north Rome, Italy). A preliminary magnetometric survey revealed the existence of anomalous zones in the analysed region. Excavation in some of the selected areas confirmed that the anomalies were generated by underground magnetic material: over 160 steel drums were found. After their removal, a new magnetometric survey was performed. On the basis of the new map, a multifrequency induction survey, a geoelectrical profile and GPR measurements were taken to extend the characterization of the subsoil

Fast geophysical prospecting applied to archaeology: results at «Villa ai Cavallacci» (Albano Laziale, Rome) site

The present essay is the result of a cooperative work between geophysicists and archaeologists in which the authors carried out an integrated geophysical prospecting in an archaeological site near Rome. This paper describes the methodology and the results of a geophysical survey carried out on Villa ai Cavallacci, an ancient roman building in Albano Laziale (Rome) discovered in the late seventies. It is often possible to obtain very important results planning a fast geophysical survey opportunely; within this framework (due to the fact that an archaeological excavation was planned in a short time), an integrated geophysical techniques survey (GPR, magnetic, and geoelectric tomography) has been carried out on the areas indicated by the archaeologists. Even if the described geophysical survey should be considered only a first step analysis, the data pointed out some very interesting features confirmed by the excavation

Location of a new ice core site at Talos Dome (East Antarctica)

In the frame of glaciology and palaeoclimate research, Talos Dome (72°48lS; 159°06lE), an ice dome on the East Antarctic plateau, represents the new selected site for a new deep ice core drilling. The increasing interest in this re- gion is due to the fact that the ice accumulation is higher here than in other domes in East Antarctica. A new deep drilling in this site could give important information about the climate changes near the coast. Previous papers showed that the dome summit is situated above a sloped bedrock. A new position on a relatively flat bedrock 5-6 km far from here in the SE direction was defined as a possible new ice core site for an European (Italy, France, Swiss and United Kingdom) drilling project named as TALDICE (TALos Dome Ice Core Project). This point, named as ID1 (159°11l00mE; 72°49l40mS), became the centre of the Radio Echo Sounding (RES) flight plan during the 2003 Italian Antarctic expedition, with the aim of confirming the new drilling site choice. In this paper 2001 and 2003 RES data sets have been used to draw a better resolution of ice thickness, bottom morphology and internal layering of a restricted area around the dome. Based on the final results, point ID1 has been confirmed as the new coring site. Fi- nally, the preliminary operations about the installation of the summer ice core camp (TALDICE) at ID1 site carried out during the XX Italian Antarctic expedition (November 2004-December 2005) are briefly described

Fourteen years of geomagnetic daily variation at Mario Zucchelli Station (Antarctica)

During the 1986-87 austral summer a geomagnetic observatory was installed at the Italian Antarctic Base Mario Zucchelli Station. In the first three years continuous time variation monitoring and absolute measurements of the geomagnetic field were carried out only during summer expeditions. Starting 1991 an automatic acquisition system, operating through all the year, was put in operation. We present here some peculiarities of the daily variation as observed for fourteen years (1987-2000). The availability of a long series of data has allowed the definition of seasonal, as well as solar cycle effects, on short time variations as observed at a cusp-cap observatory. In particular, contrary to mid latitude behaviour, a clear dependence of the daily variation amplitude on the global geomagnetic K index was well defined

Yearbook magnetic results 2015 Geomagnetic observatory of Castello Tesino

Castello Tesino observatory is one of the three geomagnetic observatories in Italy operated and maintained by the Istituto Nazionale di Geofisica e Vulcanologia. The observatory is located near the homonymous town, 55 km East from the city of Trento (Northern Italy). The observatory co-ordinates are: Geographic latitude Geographic longitude Corrected geom. latitude Corrected geom. longitude Height above mean sea level Magnetic local time midnight 46° 03 N 11° 39 E 40° 47 N 86° 23 E 1175 m 22:31 UT The corrected geomagnetic co-ordinates and the magnetic local time midnight in UT are computed using a routine available at http://modelweb.gsfc.nasa.gov and assuming the North geomagnetic pole at 82°20 N, 276°38 E. Castello Tesino Observatory has been working almost continuously since 1964 and it is considered the main Northern Italy magnetic observatory. Data from this observatory are used to study the temporal trend of the geomagnetic field in Northern Italy and to reduce magnetic field data obtained during magnetic surveys to the same period (http://roma2.rm.ingv.it/it/risorse/rete_magnetica_italiana/36/cartografia_magnetica_nazionale). The staff that collaborates to the maintenance of the observatory and in the production of Castello Tesino data set and yearbooks is: Benedetti G. absolute measurements, plots and instrument maintenance; Biasini F. absolute measurements and observatory buildings maintenance; Di Ponzio A. data processing; Fattore F. absolute measurements; Miconi M. absolute measurements; Spadoni S. data processing, data storage and data base services; Zirizzotti A. instrument maintenance This yearbook presents the results of the magnetic measurements carried out at this observatory during 2015.Istituto Nazionale di Geofisica e VulcanologiaPublished1A. Geomagnetismo e Paleomagnetism

Secular variation from the historical repeat stations of the Italian magnetic network

The study of geomagnetism OII the basis of large dat.a seeies is a very important tool: it helps to extclld our knowledge of the geomagnetic secular variatiaD ta a langet time interval aud caD bring informa'hon an geophysical phenomclla linked Dat ooly ta geomagnetism. Following these consideratioDs, we have tried ta extend the Italian repeat stations data. backwards with the indusion of the historical Italian geomagnetic data ca.talogue (Cafarella el al., 1992a). We obta.ined several data sels [rom about 1800 till nawadays for different. localities aod the analysis of secular variatioll both in space aud time over the last two centuries revealed interesting features. In this framework it Îs shown that the contribution of the observatories is very important for the accurate definition of the secular variation pattern; the study of the repeat station data together with the observatory series, can bring fundamental information to improve the knowledge of the upper core fluid flow structure that is responsible of the secular variation.Published17-281A. Geomagnetismo e PaleomagnetismoN/A or not JC