A comparison of basal reflectivity and ice velocity in East Antarctica

Jacobel, R. W.; Lapo, Karl; Stamp, J. R.; Youngblood, B. W.; Welch, Brian C.; Bamber, Jonathan

doi:10.5194/tc-4-447-2010

Cited by 34 publications

(44 citation statements)

References 23 publications

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“…Similar to the study of Wright et al (2014), our findings are consistent with criticism of interpreting surface lowering as a definitive indicator of lake drainage. Jacobel et al (2010) found high local variability in relative basal reflectivity. Those variations are only in some areas in line with a flat-lying bed reflection indicative for water.…”

Section: Trustworthiness Of the Basal Reflection Coefficientmentioning

confidence: 93%

Missing Evidence of Widespread Subglacial Lakes at Recovery Glacier, Antarctica

et al. 2018

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Recovery Glacier reaches far into the East Antarctic Ice Sheet. Recent projections point out that its dynamic behavior has a considerable impact on future Antarctic ice loss (Golledge et al., 2017, https://doi.org/10.1002/2016GL072422). Subglacial lakes are thought to play a major role in the initiation of the rapid ice flow (Bell et al., 2007, https://doi.org/10.1038/nature05554). Satellite altimetry observations have even suggested several actively filling and draining subglacial lakes beneath the main trunk (B. E. Smith et al., 2009, https://doi.org/10.3189/002214309789470879). We present new data of the geometry of this glacier and investigate its basal properties employing radio‐echo sounding. Using ice sheet modeling, we were able to constrain estimates of radar absorption in the ice, but uncertainties remain large. The magnitude of the basal reflection coefficient is thus still poorly known. However, its spatial variability, in conjunction with additional indicators, can be used to infer the presence of subglacial water. We find no clear evidence of water at most of the previously proposed lake sites. Especially, locations, where altimetry detected active lakes, do not exhibit lake characteristics in radio‐echo sounding. We argue that lakes far upstream the main trunk are not triggering enhanced ice flow, which is also supported by modeled subglacial hydrology.

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Section: Trustworthiness Of the Basal Reflection Coefficientmentioning

confidence: 93%

Missing Evidence of Widespread Subglacial Lakes at Recovery Glacier, Antarctica

et al. 2018

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“…where geometric spreading losses are [G] [Jacobel et al, 2010]. The regional attenuation correction is applied over the survey area seen in Figure 1 (250 km Â 500 km).…”

Section: Reflectivity Anomaliesmentioning

confidence: 99%

Identification and control of subglacial water networks under Dome A, Antarctica

Wolovick

Bell

Creyts

et al. 2013

J. Geophys. Res. Earth Surf.

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[1] Subglacial water in continental Antarctica forms by melting of basal ice due to geothermal or frictional heating. Subglacial networks transport the water from melting areas and can facilitate sliding by the ice sheet over its bed. Subglacial water flow is driven mainly by gradients in overburden pressure and bed elevation. We identify small (median 850 m) water bodies within the Gamburtsev Subglacial Mountains in East Antarctica organized into long (20-103 km) coherent drainage networks using a dense (5 km) grid of airborne radar data. The individual water bodies are smaller on average than the water bodies contained in existing inventories of Antarctic subglacial water and most are smaller than the mean ice thickness of 2.5 km, reflecting a focusing of basal water by rugged topography. The water system in the Gamburtsev Subglacial Mountains reoccupies a system of alpine overdeepenings created by valley glaciers in the early growth phase of the East Antarctic Ice Sheet. The networks follow valley floors either uphill or downhill depending on the gradient of the ice sheet surface. In cases where the networks follow valley floors uphill they terminate in or near plumes of freeze-on ice, indicating source to sink transport within the basal hydrologic system. Because the ice surface determines drainage direction within the bed-constrained network, the system is bed-routed but surface-directed. Along-flow variability in the structure of the freeze-on plumes suggests variability in the networks on long (10s of ka) timescales, possibly indicating changes in the basal thermal state.

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“…This reflectivity approach has been applied to several areas of Antarctica (e.g. Bentley et al, 1998;Carter et al, 2009;Christianson et al, 2012;Gades et al, 2000;Jacobel, 2010;Langley et al, 2010;Peters et al, 2005;Wright et al, 2012;Zirizzotti et al, 2012). As for methodology, accurate estimation of basal reflectivity requires calibrated radar sounding data for power detection and reliable estimates of radio-wave attenuation.…”

Section: Introductionmentioning

confidence: 99%

Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica

et al. 2012

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Abstract. In order to better understand the spatial distribution of subglacial environments, ground-based radar profiling data were analyzed for a total distance of ∼ 3300 km across Dronning Maud Land, East Antarctica. The relationship between geometrically corrected bed returned power [P c bed ] dB in decibels and ice thickness H was examined. When H is smaller than a critical value that varies according to location, [P c bed ] dB tends to decrease relatively smoothly with increasing H , which is explicable primarily by the cumulative effect of dielectric attenuation within the ice. However, at locations where H is larger than the critical H values, anomalous increases and fluctuations in [P c bed ] dB were observed, regardless of the choice of radar frequency or radar-pulse width. In addition, the amplitude of the fluctuations often range 10 ∼ 20 dB. We argue that the anomalous increases are caused by higher bed reflectivity associated with the existence of subglacial water. We used these features to delineate frozen and temperate beds. Approximately two-thirds of the investigated area was found to have a temperate bed. The beds of the inland part of the ice sheet tend to be temperate, with the exception of subglacial high mountains. In contrast, the beds of coastal areas tend to be frozen, with the exception of fast-flowing ice on the subglacial lowland or troughs. We argue that this new analytical method can be applied to other regions.

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A comparison of basal reflectivity and ice velocity in East Antarctica

Cited by 34 publications

References 23 publications

Missing Evidence of Widespread Subglacial Lakes at Recovery Glacier, Antarctica

Missing Evidence of Widespread Subglacial Lakes at Recovery Glacier, Antarctica

Identification and control of subglacial water networks under Dome A, Antarctica

Radar diagnosis of the subglacial conditions in Dronning Maud Land, East Antarctica

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