http://hdl.handle.net/2122/132 Tue, 21 May 2013 07:16:30 GMT 2013-05-21T07:16:30Z http://hdl.handle.net/2122/8440 Title: Intervento reatino "Rete WiFi" Authors: Cardinale, Vincenzo; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia Editors: Cardinale, Vincenzo Abstract: A seguito di una sequenza sismica nell’area reatina (settembre 2010) si è deciso di installare una rete temporanea che potesse aumentare in quell’area il numero di stazioni in tempo reale. Mon, 20 Dec 2010 23:00:00 GMT http://hdl.handle.net/2122/8440 2010-12-20T23:00:00Z http://hdl.handle.net/2122/8391 Title: Calving
 event 
detection 
by
 observation 
of 
seiche 
effects 
on 
the
 Greenland 
fjords Authors: Walter, F.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland; Laboratory
 of
 Hydraulics,
 Hydrology 
and
 Glaciology,
 ETH
 Zürich,
 Switzerland; Olivieri, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Clinton, J.; Swiss
 Seismological 
Service, 
ETH 
Zürich,
 Switzerland Abstract: With mass loss from the Greenland ice sheet accelerating and spreading to higher latitudes, the quantification of mass discharge in the form of icebergs has recently received much scientific attention. Here, we make use of very low frequency (0.001-0.01 Hz) seismic data from three permanent broadband stations installed in the summers of 2009/2010 in northwest Greenland in order to monitor local calving activity. At these frequencies, calving seismograms are dominated by a tilt signal produced by local ground flexure in response to fjord seiching generated by major iceberg calving events. A simple triggering algorithm is proposed to detect calving events from large calving fronts with potentially no user interaction. Our calving catalogue identifies spatial and temporal differences in calving activity between Jakobshavn Isbræ and glaciers in the Uummannaq district some 200 km further north. The Uummannaq glaciers show clear seasonal fluctuations in seiche-based calving detections as well as seiche amplitudes. In contrast, the detections at Jakobshavn Isbræ show little seasonal variation, which may be evidence for an ongoing transition into winter calving activity. The results offer further evidence that seismometers can provide efficient and inexpensive monitoring of calving fronts. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8391 2011-12-31T23:00:00Z http://hdl.handle.net/2122/7273 Title: Ice and Bedrock Characteristics Underneath Dome C (Antarctica) From Radio Echo Sounding Data Analysis Authors: Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: The Radio Echo Sounding (RES) system is one of the most widely used active remote sensing techniques for polar ice sheet exploration, including bedrock morphology studies and subglacial lake investigations. Recently, bedrock characterization has been improved through the analysis of radar echo strength. The analysis of the RES signal amplitude has been used to highlight areas of high reflectivity variation, attributable to wet ice-bedrock interfaces. In a previous paper the authors described a method to distinguish a wet or dry bedrock-ice interface by analyzing RES data and introducing a linear model for internal ice absorption. In the following paper this subject is reconsidered in greater depth, taking into account important aspects not considered in the previous paper. In particular, a comparison between the ice absorption rate from RES measurements and from EPICA ice core conductivity data was proposed. Moreover, the signal amplitude contributions of internal ice layers and different kinds of rock interface were evaluated. Encouraged by these results, further data analysis produced a new version of the bedrock reflectivity variation map of the Dome C area. The map confirms a wide dispersion of wet/dry rock interfaces in the area studied, indicating the possibility of flowing water along both sides of the Concordia Trench. Sun, 31 Jul 2011 22:00:00 GMT http://hdl.handle.net/2122/7273 2011-07-31T22:00:00Z http://hdl.handle.net/2122/6897 Title: Microwave Signature of the Greenland Ice Sheet at Ku- and S-Bands Authors: Bignami, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Pierdicca, N.; La Sapienza University of Rome; Pulvirenti, L.; La Sapienza University of Rome Abstract: This letter is focused on the microwave signature characterization of the Greenland ice sheet. Such characterization is carried out by exploiting the S- and Ku-band brightness temperatures measured by the radar altimeter RA-2 when it operates as a radiometer during the ENVISAT Commissioning Phase for the purpose of calibrating the receiver. Despite the poor radiometric resolution and the calibration issues, this activity represented a unique opportunity to gather brightness temperatures at frequencies that are not available from current spaceborne microwave radiometers. The analysis of the passive RA-2 data investigates the influence of terrain height and of the temperature of the snow layers on the brightness temperatures at RA-2 bands. The effect of the different penetration depths of the electromagnetic radiation at S- and Ku-bands is also pointed out. Measurements from the Advanced Microwave Scanning Radiometer for the Earth Observing System are used to complement the data provided by RA-2 and to verify their reliability Tue, 31 Mar 2009 22:00:00 GMT http://hdl.handle.net/2122/6897 2009-03-31T22:00:00Z http://hdl.handle.net/2122/6244 Title: GPR as an effective tool for safety and glacier characterization: experiences and future development Authors: Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: In recent times, the GPR technique has assumed an important role in glacial environment exploration. Ice thickness, bedrock description, internal water floods or underground channel, glacial structures (as snow layering and crevasses detection) form part of our experience in Antarctica and in high alpine glacier ski areas. In this paper, we present some results of these investigations exploring the possibility of combining our technical expertise on Radio Echo Sounding (RES) instrumentation to develop a system for subglacial environment exploration. Sat, 31 Jul 2010 22:00:00 GMT http://hdl.handle.net/2122/6244 2010-07-31T22:00:00Z http://hdl.handle.net/2122/6242 Title: Effect of blowing snow on surface mass balance of East Antarctica Authors: Frezzotti, M.; ENEA, Laboratory for climate observations, Roma, Italy; Scarchilli, C.; ENEA, Laboratory for climaDipartimentote observations, Roma, Italy and; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: In the convergence slope/coastal areas of Antarctica, a large fraction of snow is continuously eroded and exported by wind to the atmosphere and into the ocean. The extreme environmental conditions and remote location of Antarctica have long inhibited the systematic study of its climate and snow accumulation processes. Measurement of blowing snow in Antarctica is very difficult and limited, and data are only available for a few sites. Atmospheric models estimate that the horizontal divergence of snow by wind transport is of minor significance for integrated ice sheet surface mass balance because the model simulations assume that katabatic winds tend to remove mass from the interior regions of the continent and displace it to coastal/convergence areas. Moreover, the blowing snow process and direct export into the ocean are not explicitly included in numerical weather forecasting and general circulation models. Blowing snow transport and erosion from instruments, snow radar and satellite images were acquired in East Antarctica. Extensive presence of ablation surface (blue ice and wind crust) upwind and downwind of the measurement site suggest that the combine processes of blowing snow sublimation and snow transport remove up to 50% of the precipitation in the coastal and slope convergence area. These phenomena represent a major negative effect on the snow accumulation, and they are not sufficiently taken into account in studies of surface mass balance. The observed wind-driven ablation explains the inconsistency between atmospheric model precipitation and measured snow accumulation value. Sat, 01 May 2010 22:00:00 GMT http://hdl.handle.net/2122/6242 2010-05-01T22:00:00Z http://hdl.handle.net/2122/6214 Title: Dry-wet bedrock interface detection by radio echo sounding measurements Authors: Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Tabacco, I. E.; Univ. di Milano - Sezione Geofisica, Milan, Italy; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Mangialetti, M.; Univ. di Milano - Sezione Geofisica, Milan, Italy; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: In this paper a method to distinguish a wet or dry bedrock-ice interface is proposed. It is based on the analysis of Radio Echo Sounding (RES) measurements, a widely employed method for determining bedrock topography in Antarctica. In particular, the RES system has played an important role in subglacial lake exploration and hydrogeological studies at the bedrock-ice interface. Recently, bedrock characterization has been improved through the analysis of the power of radar echoes. Signal power depends on bedrock reflectivity and its specific physical condition. In this paper a linear model describing the loss term (internal ice absorption) is proposed. This model, together with other known quantities, contributes towards an assessment of power variation of bedrock reflectivity in order to determinate wet and dry bedrock interfaces in the Dome C region in Antarctica. Wed, 31 Mar 2010 22:00:00 GMT http://hdl.handle.net/2122/6214 2010-03-31T22:00:00Z http://hdl.handle.net/2122/5891 Title: Radar systems for Glaciology Authors: Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Urbini, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Cafarella, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Baskaradas, J. A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Editors: Kouemou, G. Abstract: 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. Thu, 31 Dec 2009 23:00:00 GMT http://hdl.handle.net/2122/5891 2009-12-31T23:00:00Z http://hdl.handle.net/2122/5888 Title: La radiopropagazione nei ghiacciai Authors: Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Sciacca, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia Abstract: Da alcuni anni l'INGV sta partecipando a progetti di ricerca nel campo della radioglaciologia, cioè lo studio dei ghiacciai tramite sistemi radar conosciuti anche come Radio Echo Sounding. Gli esiti del lavoro svolto in Istituto e i risultati delle campagne hanno portato alla pubblicazione di alcuni lavori, la formulazione dei quali ha richiesto lo svolgimento preventivo di considerazioni teoriche e l'approntamento di procedure di calibrazione. Queste considerazioni sono raccolte nel presente lavoro. Tue, 31 Dec 2002 23:00:00 GMT http://hdl.handle.net/2122/5888 2002-12-31T23:00:00Z http://hdl.handle.net/2122/4082 Title: Analysis of bottom morphology of the David Glacier-Drygalski Ice Tongue, East Antarctica Authors: Tabacco, I. E.; Sezione Geofisica, Dipartimento di Science della Terra, Università degli Studi di Milano, I-20129 Milano, Italy; Bianchi, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Chiappini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zirizzotti, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Zuccheretti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia Abstract: Data from radio-sounding measurements have been analysed to determine the ice thickness and the bottom morphology of Drygalski Ice Tongue, Antarctica. The morphology and the structure of the bottom surface has been studied through an electromagnetic interpretation. A function that includes the gain/loss due to the geometrical shape of the reflecting surfaces has been calculated. Such a function has been evaluated assuming some physical electromagnetic quantities (the temperature of the glacier, the complex dielectric permittivity of ice, sea ice and sea water). The ice-water interface shows both concave and convex faces toward the sounding system, producing a focusing or defocusing effect, detected as absolute (or relative) amplitude variation in the echo signal. It is shown that the calculated function follows quite well the observed bottom rippled surface of the glacier tongue estimated from the time-arrival measurements of the echo signal. Fri, 31 Dec 1999 23:00:00 GMT http://hdl.handle.net/2122/4082 1999-12-31T23:00:00Z