UHF radar system for airborne surveys of ice thickness

Narod, B. Barry

doi:10.1139/e83-096

Cited by 12 publications

(10 citation statements)

References 30 publications

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“…The system performance is 126 dB and data are recorded on magnetic tape. Full descriptions of the radar and recording system are given by Narod and Clarke (1983). The 1981 Ellesmere Island survey was flown from a Canadian Forces Twin Otter onto which a 90" comer-reflecting antenna had been attached (Narod and Clarke 1983, Fig.…”

Section: Data Collectionmentioning

confidence: 99%

“…For these flights, traces of 10 ps duration were recorded at a rate of 10 tracesls. (The UBC radar takes samples at a constant rate (Narod and Clarke 1983); there is a resulting trade-off between trace length and trace repetition rate. Trace length is selected to match the expected ice depths.)…”

Section: Data Collectionmentioning

confidence: 99%

“…i Propagation and reflection loss The standard "radar equation" (e.g., Skolnik 1962;Bogorodsky et al 1985) rewritten in the form (Narod and Clarke 1983) allows PRC and loss rate to be estimated. In [I], P T is the indicated input power to the receiver; P, is the transmitted power; G is the antenna gain; X is the wavelength in air; C is the sum (in decibels) of all system losses; T2 is the power transmission coefficient in the air-ice interface; r' = za + ziln is the target range adjusted for refraction at the air-ice interface; R2 is the power reflection coefficient for a plane reflecting target; D is the one-way propagation loss rate (in decibels per metre); the constant A = (In 10)llO = 0.2303 has been introduced to simplify conversion of [I] to an equivalent equation involving decibels; A has the useful property that 10 loglo (exp A ) = 1.…”

Section: Reflector Rangementioning

confidence: 99%

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Airborne UHF radar sounding of glaciers and ice shelves, northern Ellesmere Island, Arctic Canada

Narod¹,

Prager²

1988

Can. J. Earth Sci.

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More than 2000 line-kilometres of ice were sounded in 1981 using an 840 MHz pulsed radar system. The surveyed regions include Mt. Oxford ice cap, Disraeli Glacier, Milne Glacier, Ward Hunt Ice Shelf, and Milne Ice Shelf in northern Ellesmere Island, Arctic Canada. The maximum ice thickness that was reliably recorded was 750 m for Milne Glacier. In addition to ice thickness interpretation, the power reflection coefficient (PRC) and propagation loss rate were estimated from the data. Measured basal PRC's differ for ice shelves, floating glaciers, and grounded glaciers. Spatial variations of PRC have been used to infer a composite structure for the ice shelves. Ward Hunt Ice Shelf proved difficult to sound, probably because of its known saline and bxackish chemistly. Excellent results were obtained for Milne Ice Shelf and its depth was found to average roughly 70 m, in places attaining 100 m. Bottom-side crevasses were observed within Milne Ice Shelf. The characteristic ridge and trough topography of the ice shelf surface has little or no bottom-side expression.Des sondages sur plus de 2000 lignes-kilomktres de glace ont CtC effectuCs en 1981 par impulsion radar de 840 MHz. L'acquisition des donnCes couvre les regions de la calotte glaciaire Mt. Oxford, du glacier Disraeli, du glacier Milne, de la plate-forme de glace Ward Hunt, et de la plate-forme de glace Milne dans la partie nord de l'ile Ellesmere, dans 1'Arctique canadien. L'Cpaisseur maximale de la glace qui a kt6 enregistke avec prkcision Ctait de 750 m pour le glacier Milne. En plus de I'interprCtation de I'Cpaisseur de la glace, ces donnCes ont permis d'kvaluer le coefficient du pouvoir de reflexion (CPR) et la fiuction du taux de propagation. Les valeurs mesurCes des CPR different selon qu'il s'agit de plates-forrnes de glace, de glaciers flottants ou de glaciers ancks au sol. Les variations spatiales des CPR ont kt6 utilisCes pour Claborer une structure composite des plates-fonnes de glace. La plate-forme de glace Ward Hunt s'est avCke difficile a sonder, probablement B cause de la pksence connue de sel et d'une chimie saumstre. Des rCsultats excellents ont Ct C obtenus pour la plate-forme Milne et sa profondeur correspond en moyenne a 70 m, a certains endroits elle atteint 100 m. Des crevasses 1atCrales de fond ont CtC observCes t i I'intCrieur de la plate-forme de glace Milne. La crete et la topographie en creux caractkristiques de la surface de la plate-forme de glace ne sont pas, ou seulement peu, exprimkes par la pksence de crevasses laterales de fond.[Traduit par la rewe]Can. J. Earth Sci. 25, 95-105 (1988)

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Section: Data Collectionmentioning

confidence: 99%

Section: Data Collectionmentioning

confidence: 99%

Section: Reflector Rangementioning

confidence: 99%

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Airborne UHF radar sounding of glaciers and ice shelves, northern Ellesmere Island, Arctic Canada

Narod¹,

Prager²

1988

Can. J. Earth Sci.

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“…The Grant Land Mountains rise abruptly from the north shore of Lake Hazen (157 m above sea level (asl)), reaching 2665 m asl (Barbeau Peak). They support a large ice cap up to 900 m thick, from which trunk glaciers descend to 560-240 m asl near Lake Hazen (Hattersley-Smith et al 1969;Narod and Clarke 1983). The mountains trend southwest-northeast along the structural grain and are formed of Paleozoic limestone, sandstone, slate, and chert pebble conglomerate (Christie 1964;Trettin 1994).…”

Section: Physiography and Climatementioning

confidence: 99%

Late Quaternary glacial history of Lake Hazen Basin and eastern Hazen Plateau, northern Ellesmere Island, Nunavut, Canada

Smith¹

1999

Can. J. Earth Sci.

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The glacial history of the broad interior of northeastern Ellesmere Island is first documented here. Studies of glacial geomorphology and marine and lacustrine sedimentology indicate that the region was inundated by cold-based ice emanating from the Grant Land Mountains sector of the Innuitian Ice Sheet during the last glacial maximum. Retreat of coalescent, marine-based Ellesmere and Greenland ice from Robeson Channel had started by 10.1 ka BP and reached the mouths of many fiords along southeast Hazen Plateau by 8 ka BP. Proglacial meltwater channels emanating from plateau ice caps, crosscut lateral meltwater channels marking the retreat of Grant Land Mountain ice. The crosscutting is interpreted to reflect an early Holocene growth of plateau ice caps concurrent with the retreat of marinebased margins. This suggests that initial regional ice retreat was eustatically controlled. Stabilization of glacier margins at the heads of fiords occurred by 7.5-7 ka BP, after which land-based margins retreated as little as 10 km by 6 ka BP. Across much of northeastern Hazen Plateau, however, Grant Land Mountain ice retreated more rapidly. This more rapid retreat was accentuated by the impoundment of proglacial lakes against the plateau to the south and the subsequent breakup of ice by calving. Glaciers continued to occupy much of Lake Hazen Basin at 5.3 ka BP, after which they broke up rapidly in a proto-Lake Hazen, retreating to margins at, or behind, those of the present by 5 ka BP.Résumé : L'histoire glaciaire de la large région intérieure du nord-est de l'île d'Ellesmere est reconstituée ici pour la première fois. Les études de la géomorphologie glaciaire et de la sédimentologie marine et lacustre indiquent que la région fut envahie par un glacier à base froide qui émanait du secteur des monts Grand Land, de l'Inlandsis Innuitien, durant l'apogée du Dernier Glaciaire. La régression dans le chenal de Robeson du glacier formé de l'union des glaciers d'Ellesmere à base marine et de Groenland, a débuté vers 10,1 ka avant le Présent; et vers 8 ka avant le Présent la marge du glacier avait reculé jusqu'aux embouchures de nombreux fjords localisés le long de la région sud-est du Plateau de Hazen. Les chenaux proglaciaires écoulant l'eau de fonte issue des calottes glaciaires du plateau recoupaient les chenaux latéraux chargée d'eau de fonte dérivée du glacier du mont Grand Land. Ce recoupement des chenaux reflète la croissance des calottes glaciaires sur le plateau durant l'Holocène précoce, concurremment au retrait des marges à base marine. Ce qui suggère que le retrait initial du glacier dans la région était sous influence eustatique. La stabilisation des marges des glaciers à la tête des fjords est apparue vers 7,5-7 ka avant le Présent, par la suite les marges glaciaires basées sur terres avaient régressé à peine de 10 km vers 6 ka avant le Présent. Cependant, dans une bonne partie du nord-est du Plateau de Hazen le glacier du mont Grant Land régressait plus rapidement. Ce retrait plus rapide fut accéléré par l'endiguement...

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“…The ice thickness of Canadian High Arctic ice caps has been measured by radio-echosounding techniques (Hattersley-Smith and others, 1969;Paterson and Koerner, 1974;Koerner, 1977b;Oswald, 1975;Narod and Clarke, 1983). Unpublished work was done as well by the Scott Polar Research Institute at the top of Devon Ice Cap in 1974; the work is available as maps at the GSC.…”

Section: Thicknessmentioning

confidence: 99%