Using radar-sounding data to identify the distribution and sources of subglacial water: application to Dome C, East Antarctica

Carter, Sasha Peter; Blankenship, D. D.; Young, D. A.; Holt, J. W.

doi:10.3189/002214309790794931

Cited by 65 publications

(70 citation statements)

References 73 publications

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“…Finally, basal melt rates for the region north of Dome C have been estimated by fitting the vertical strains with dated radar layers, to constrain the vertical advection of ice, and its energy budget (Carter et al, 2009). The uncertainty of the GF estimation was ±12 mW m −2 , which is a significant improvement over the previous estimations but is still too large to identify a location with very old ice.…”

Section: Assessing Gf Under Ice Sheetsmentioning

confidence: 99%

Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling

et al. 2017

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Abstract. Basal melt rate is the most important physical quantity to be evaluated when looking for an old-ice drilling site, and it depends to a great extent on the geothermal flux (GF), which is poorly known under the East Antarctic ice sheet. Given that wet bedrock has higher reflectivity than dry bedrock, the wetness of the ice-bed interface can be assessed using radar echoes from the bedrock. But, since basal conditions depend on heat transfer forced by climate but lagged by the thick ice, the basal ice may currently be frozen whereas in the past it was generally melting. For that reason, the risk of bias between present and past conditions has to be evaluated. The objective of this study is to assess which locations in the Dome C area could have been protected from basal melting at any time in the past, which requires evaluating GF. We used an inverse approach to retrieve GF from radarinferred distribution of wet and dry beds. A 1-D heat model is run over the last 800 ka to constrain the value of GF by assessing a critical ice thickness, i.e. the minimum ice thickness that would allow the present local distribution of basal melting. A regional map of the GF was then inferred over a 80 km × 130 km area, with a N-S gradient and with values ranging from 48 to 60 mW m −2 . The forward model was then emulated by a polynomial function to compute a timeaveraged value of the spatially variable basal melt rate over the region. Three main subregions appear to be free of basal melting, two because of a thin overlying ice and one, north of Dome C, because of a low GF.

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Section: Assessing Gf Under Ice Sheetsmentioning

confidence: 99%

Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling

et al. 2017

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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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“…channelised versus distributed systems: see Mair, Nienow, Sharp, Wohlleben, & Willis, 2002;Walder & Fowler, 1994) are mostly remote or indirect and include, for example, radar sounding (e.g. Carter, Blankenship, Young, & Holt, 2009), dyetracing (e.g. Schuler & Fischer, 2009), remote sensing (e.g.…”

Section: Introductionmentioning

confidence: 99%

A map of large Canadian eskers from Landsat satellite imagery

2013

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Meltwater drainage systems beneath ice sheets are a poorly understood, yet fundamentally important environment for understanding glacier dynamics, which are strongly influenced by the nature and quantity of meltwater entering the subglacial system. Contemporary sub-ice sheet meltwater drainage systems are notoriously difficult to study, but we can utilise exposed beds of palaeo-ice sheets to further our understanding of subglacial drainage. In particular, eskers record deposition in glacial drainage channels and are widespread on the exposed beds of former ice sheets. This paper presents a 1:5,000,000 scale map of .20,000 large eskers (typically . 2 km long) deposited by the Laurentide Ice Sheet (LIS), mapped from Landsat imagery of Canada, in order to establish a dataset suitable for analysis of esker morphometry and drainage patterns at the ice sheet scale. Comparisons between eskers mapped from Landsat imagery and aerial photographs indicate that, in most areas, approximately 75% of eskers are detected using Landsat. The data presented in this map build on and extend previous work in providing a consistent map of an unprecedented sample of eskers for quantitative analysis. It offers an alternative perspective on the problems surrounding ice-sheet meltwater drainage and can be used for: (i) detailed investigations of esker morphometry and distribution from a large sample size; (ii), testing of numerical models of meltwater drainage routing that predict esker characteristics (e.g. channel spacing, sinuosity), (iii) assessment of the factors that control esker location and formation; and (iv), a refined understanding of ice margin configurations during retreat of the LIS.

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Using radar-sounding data to identify the distribution and sources of subglacial water: application to Dome C, East Antarctica

Cited by 65 publications

References 73 publications

Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling

Geothermal flux and basal melt rate in the Dome C region inferred from radar reflectivity and heat modelling

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

A map of large Canadian eskers from Landsat satellite imagery

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