Radio-Echo Sounding: Reflections From Internal Layers In Ice Sheets

Clough, John W.

doi:10.1017/s002214300002147x

Cited by 44 publications

(29 citation statements)

References 15 publications

(2 reference statements)

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“…), and in structure (ice crystal orientation, content and size of air bubbles in the ice) from the rest of the glacier ice. Similar internal reflections have been often observed in Antarctica and Greenland (Bogorodskiy, 1975;Paren and Robin , 1975 ;Gudmandsen, 1975;Clough, 1977 ;Ackley and Keliher, 1979). It is most probable that they are associated with internal layers which were formed in the past during periods of climatic warming (Robin and others, 1969 ;Whillans, 1976).…”

Section: Internal Structure and Ice Volume Of The Svalbard Glacierssupporting

confidence: 72%

Radio Echo-Sounding of Svalbard Glaciers

Macheret¹,

Zhuravlev²

1982

J. Glaciol.

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ABSTRACT. Peculiarities of radio echo-sounding of mountain glaciers and ice fields between nunataks from terrestrial vehicles and from helicopters are considered in this paper. The possibility of using comparatively high frequencies (of up to 865 MHz) for sounding such glaciers is demonstrated on the basis of experimental data. Results of airborne radio echo-sounding of Svalbard glaciers of various types, dimensions, and regime obtained with the help of the 620 M Hz airborne equipment of high resolution are shown. Returns from the glacier bed have been obtained on the majority of glaciers under investigation. The firn regions of ice fields with temperate regimes flowing between nunataks are, mostly, an exception. Depression in the glacier bed with the ice thickness up to 540 m, as well as internal reflecting boundaries have been detected in some glaciers. Ice volumes of glaciers have been determined from the airborne radio echo-sounding data with the use of a parabolic approximation to the cross-section glacier profiles. Good correlational dependence between ice volume and surface area of glaciers has been established and is used to estimate the ice and water resources in Svalbard glaciers. RESUME. Sondages par echo-radio des glaciers du Sualbard. Dans cet article on examine les particularites des sondages par echo-radio de glaciers de type de montagne ou de piedmont depuis des vehicules terrestres ou par helicoptere. Sur la base des donnees experimentales on montre une possibilite d'utiliser a titre de comparaison des hautes frequences (jusqu 'a 865 MHz) pour sonder de tels glaciers. On donne et on discute les resultats de sondages aeriens par echo-radio des glaciers du Svalbard de type montagne, piedmont et calotte, avec des appareils de 620 MHz a gran de capacite de resolution spatiale. Des signaux rI:flechis sur le lit du glacier ont ete recueillis sur la majorite des glaciers sondes. Les zones de neves des glaciers de type piedmont avec des regimes thermiques " chauds" (glaciers temperes) sont, la plupart du temps , une exception. On a decouvert sur une serie de glaciers des depressions du fond du lit avec des valeurs de l'epaisseur de glace allant jusqu' a 540 m, ainsi que des pi ages de reflexion interne. A partir de sondages par echo-radio en utilisant une approximation parabolique pour les profils des sections transversales d'un glacier on a pu determiner les volumes des glaciers et etablir une bonne correlation avec la surface englacee. On en a tire une estimation des ressources en glace et en eau des glaciers du Svalbard.

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Section: Internal Structure and Ice Volume Of The Svalbard Glacierssupporting

confidence: 72%

Radio Echo-Sounding of Svalbard Glaciers

Macheret¹,

Zhuravlev²

1982

J. Glaciol.

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“…It is widely accepted that permittivity changes due to density [ Robin et al , 1969; Clough , 1977], hereinafter P D ( P for permittivity, D for density), and conductivity changes due to acidity [ Millar , 1981], hereinafter C A , are causes of internal reflections. In addition, permittivity changes due to COF, hereinafter P COF , are a third cause of internal reflections; this source arises from the dielectric anisotropy of single crystal ice [ Fujita et al , 1993].…”

Section: Introductionmentioning

confidence: 99%

Crystal orientation fabrics within the Antarctic ice sheet revealed by a multipolarization plane and dual‐frequency radar survey

et al. 2003

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[1] To investigate the viscosity structure of ice sheets induced by crystal orientation fabric (COF), we carried out a multipolarization plane and dual-frequency radar survey in East Antarctica. Radar surveys were done along a 670-km-long flow line from Dome Fuji toward the coast and two transverse lines of 300-km and 20-km length, respectively. The radar echoes were highly dependent on the polarization plane for ice depths between about 40 and 60% of the ice thickness in the lower reaches of the convergent ice flow sector approaching the outlet glacier. When the polarization was perpendicular to the ice flow, echoes were about 10 dB stronger than when the polarization was parallel to the ice flow. This feature was not clear in the upper part of this convergent flow sector. Farther inland, where ice flow is divergent or parallel, the radar echo varied by several decibels because of changes of the radar polarization and had maxima in two orientations. Dual-frequency data showed that the cause of the reflections was changes in COF. Multipolarization data identified anisotropic reflectivities and birefringence as causes of the anisotropic radar echoes in the lower and upper reaches, respectively. With the aid of ice-core-based studies on COF, we show that ice is composed of stacked layers of single-pole and vertical girdle fabrics in the lower reaches. In contrast, we argue that changes of single-pole clustering cause isotropic reflectivities in the upper reaches. We also discuss on the development of COF along ice flow and its implication to ice sheet dynamics.INDEX TERMS: 0669 Electromagnetics: Scattering and diffraction; 0933 Exploration Geophysics: Remote sensing; 1827 Hydrology: Glaciology (1863); 6969 Radio Science: Remote sensing; KEYWORDS: ice-penetrating radar, internal layers Citation: Matsuoka, K., T. Furukawa, S. Fujita, H. Maeno, S. Uratsuka, R. Naruse, and O. Watanabe, Crystal orientation fabrics within the Antarctic ice sheet revealed by a multipolarization plane and dual-frequency radar survey,

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“…Parcn and Robin, 1975;Clough, 1977 Z2, from a side of an enclosing layer with bulk impedance Z1, the power-reflection coefficient (PRC) has been given by Paren and Robin (1975) and Paren (1981) Parcn and Robin (1975) and Parcn (1981) as PRC due to changes in conductivity ansmg from the changes in acidity is calculated using Equations (la) and (3). A difference in phase by r./2 occurs between the return signals of radio echo due to changes in conductivity in Equation (3) and those due to changes in permittivity in Equation (2) (\:loore, 1988).…”

Section: Introductionmentioning

confidence: 99%

“…However, this was not supported, mainly because the dielectric anisotropy of ice, the difference between elle, e' parallel to the c axis and e1-c, e' perpendicular to the c axis, was unknown quantitatively at frequencies used in RES until recently. Clough (1977) estimated that sharp changes in crystal orientation may produce significant reflection coetlicients if the anisotropy is as high as 1%. Gow and Wi11iamson (1976) showed examples of sharp changes in crystal orientation.…”

Section: Introductionmentioning

confidence: 99%

Causes and nature of ice-sheet radio-echo internal reflections estimated from the dielectric properties of ice

Fujita¹,

Mae²

1994

A. Glaciology.

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ABSTRACT. The causes and nature of ice-sheet radio-echo internal reflections at deep layers in polar icc sheets arc discussed, based on the dielectric properties of ice that have been measured at microwave frequency and radio freq uency. The reflection coefficients of electromagnetic waves in ice sheets due to two causes the change in permittivity induced by changes in crystal-orientation fabrics with depth, and changes in conductivity induced by changes in acidity with depth -were derived respectively as a [uIJction of the frequency used in radar sounding and the temperature of ice, and both were compared quantitatively.

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Radio-Echo Sounding: Reflections From Internal Layers In Ice Sheets

Cited by 44 publications

References 15 publications

Radio Echo-Sounding of Svalbard Glaciers

Radio Echo-Sounding of Svalbard Glaciers

Crystal orientation fabrics within the Antarctic ice sheet revealed by a multipolarization plane and dual‐frequency radar survey

Causes and nature of ice-sheet radio-echo internal reflections estimated from the dielectric properties of ice

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