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

Fujita, Shujl; Mae, Shy"ji

doi:10.3189/172756494794587311

Cited by 44 publications

(56 citation statements)

References 23 publications

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“…Together these surfaces define the 3D structure of the NPP. Similarly to the interpretation of MARSIS data at the south pole of Mars [11], we determine the surface elevation map for laterally extensive internal reflectors.…”

Section: Methodsmentioning

confidence: 99%

“…In contrast, internal reflections in terrestrial ice sheets are correlated with variations in density, acidity, and crystalorientation fabric, with acidity having the dominant effect at frequencies below ~60 MHz [11]. The Mars polar materials are being investigated at frequencies of 20 MHz (SHARAD) and 1.3-5.5 MHz (MARSIS), with reflectors detected to depths of more than 3 km [4,12].…”

Section: Introductionmentioning

confidence: 98%

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Structure of the basal unit of the North Polar Plateau of Mars, from MARSIS

Selvans

Aharonson

Plaut

et al. 2009

2009 IEEE Radar Conference

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We use 36 MARSIS orbits to extract reflector depths for laterally extensive internal surfaces in the North Polar Plateau and compare the interpolated surface at the bottom of the ice to a prediction of that surface using MOLA data. We find that the prediction and data are in good agreement in terms of regional slope, and may even agree on the finer-scale saddle feature expected based on MOLA. We conclude that the underlying plains are not deflected anywhere beneath the ice deposits, and infer a possibly atypical composition or texture at the top of the Basal Unit in the 270° longitude direction, perhaps indicative of a paleo-dunefield.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 98%

Structure of the basal unit of the North Polar Plateau of Mars, from MARSIS

Selvans

Aharonson

Plaut

et al. 2009

2009 IEEE Radar Conference

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“…Ice-penetrating radar surveys of polar ice sheets commonly reveal spatially coherent internal layering. The 'layers' are widely recognized as isochrons since they likely result from depositional processes, shallow layers (<500-1000 m) being primarily due to ice density variations while at greater depths they are likely due to acidic fallout from volcanic eruptions and/or changes in impurity concentration associated with climatic transitions (Hammer 1980;Fujita and Mae 1994). The layer pattern deep in the ice column is often complicated by flow over basal topography; but near the surface, the relative depths and thickness of the layers are controlled primarily by burial rate.…”

Section: Radar Stratigraphymentioning

confidence: 99%

Accumulation Rate Measurements at Taylor Dome, East Antarctica: Techniques and Strategies for Mass Balance Measurements in Polar Environments

Morse¹,

Waddington²,

Marshall³

et al. 1999

Geografiska Annaler A

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1999:Accumulation rate measurements at Taylor Dome, East Antarctica: techniques and strategies for mass balance measurements in polar environments. Geogr. Ann., 81 A (4): 683-694.ABSTRACT. Accumulation rate measurements on the East Antarctic plateau are challenging due to both spatial and temporal variability. Annual stratigraphy is often not reliably or consistently preserved in the firn, and so accumulation cannot be determined from snow pit stratigraphy. We present a suite of accumulation rate measurements collected over several seasons at Taylor Dome, East Antarctica. We compare net accumulation results from direct burial rate measurements and ß-activity firn cores along a 35 km traverse. The two methods are consistent and show that the net accumulation varies from greater than 10 cm a -1 to about 1 cm a -1 (ice equivalent) southwest to northeast across the dome. We map the depth of shallow radar layering to interpolate and extrapolate these point-location measurements and show that considerable variations occur over kilometer scales resulting from subtle surface topography. We also present accumulation rates estimated from concentration of the cosmogenic isotope 10 Be and from activity profiles of 210 Pb. Finally, satellite passive microwave data are used to estimate spatially averaged accumulation rates on the regional to continental scale to provide a context for these local observations. We show that robust mass balance measurements in this environment must rely on spatial and/or temporal averaging.

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“…These reflecting horizons have been attributed to various features such as layers of differing density [cf. Paren and Robin, 1975;Clough, 1977] and layers of acidity due to volcanic eruptions [Hammer, 1980;Millar, 1981] and to changes in ice crystal fabric Fujita and Mae, 1994].…”

Section: Introductionmentioning

confidence: 99%

Spatial distribution of snow in western Dronning Maud Land, East Antarctica, mapped by a ground‐based snow radar

Richardson¹,

Aarholt²,

Hamran³

et al. 1997

J. Geophys. Res.

103

123

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Abstract. During the austral summer 1993/1994, the spatial distribution of snow was mapped by a ground-based snow radar (800-2300 MHz) in western Dronning Maud Land, East Antarctica. Snow radar soundings were performed along continuous profiles extending from the ice shelf up to the polar plateau, a total distance of 1040 km. The high-resolution radar registrations revealed subsurface layering in the uppermost 12 m of the snowpack. The travel time record was translated into snow accumulation expressed in water equivalents, based on an empirical relationship between wave speed and firn density. A good knowledge on snow density variations with depth is essential for the variability studies. Generally, the snow layering was well developed in the coastal area and less well developed on the polar plateau. High spatial variability in snow accumulation was observed on a regional as well as on a local scale. The variability was very high in areas with large surface slopes, such as the grounding zone and around nunataks. The highest variability was recorded in the nunatak area, where the standard deviation reached 59% of the spatial average accumulation. On the smooth high-altitude plateau, variations in accumulation were less pronounced. However, here the standard deviation exceeded 22% of the average accumulation rate. Provided that the snow radar soundings are supported by dating of reference horizons along the travel route, this is a good method to obtain the accumulation rate and pattern for large areas with a high spatial resolution.

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

Cited by 44 publications

References 23 publications

Structure of the basal unit of the North Polar Plateau of Mars, from MARSIS

Structure of the basal unit of the North Polar Plateau of Mars, from MARSIS

Accumulation Rate Measurements at Taylor Dome, East Antarctica: Techniques and Strategies for Mass Balance Measurements in Polar Environments

Spatial distribution of snow in western Dronning Maud Land, East Antarctica, mapped by a ground‐based snow radar

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