How dynamic are ice-stream beds?

Davies, Damon; Bingham, Robert G.; King, Edward C.; Smith, Andrew M.; Brisbourne, Alex; Spagnolo, Matteo; Graham, Alastair G C; Hogg, Anna E.; Vaughan, David G.

doi:10.5194/tc-12-1615-2018

Cited by 13 publications

(8 citation statements)

References 104 publications

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“…Future surveys are unlikely to resemble those conducted previously since ice-sheet models require that data are collected with strategies optimized for their purpose, including flowlines for process interpretation, ground-based time-series for local process monitoring, and repeat flights (Kingslake and others, 2014; Nicholls and others, 2015; Chu and others, 2016; Khazendar and others, 2016; Holschuh and others, 2017; Davies and others, 2018; Schroeder and others, 2018; Young and others, 2018; Bartlett and others, 2020). These process- and site-specific surveys can also take advantage of systems with wider bandwidths and larger antenna arrays that provide enhanced performance, but with more limited range (e.g.…”

Section: Datamentioning

confidence: 99%

Five decades of radioglaciology

et al. 2020

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Radar sounding is a powerful geophysical approach for characterizing the subsurface conditions of terrestrial and planetary ice masses at local to global scales. As a result, a wide array of orbital, airborne, ground-based, and in situ instruments, platforms and data analysis approaches for radioglaciology have been developed, applied or proposed. Terrestrially, airborne radar sounding has been used in glaciology to observe ice thickness, basal topography and englacial layers for five decades. More recently, radar sounding data have also been exploited to estimate the extent and configuration of subglacial water, the geometry of subglacial bedforms and the subglacial and englacial thermal states of ice sheets. Planetary radar sounders have observed, or are planned to observe, the subsurfaces and near-surfaces of Mars, Earth's Moon, comets and the icy moons of Jupiter. In this review paper, and the thematic issue of the Annals of Glaciology on ‘Five decades of radioglaciology’ to which it belongs, we present recent advances in the fields of radar systems, missions, signal processing, data analysis, modeling and scientific interpretation. Our review presents progress in these fields since the last radio-glaciological Annals of Glaciology issue of 2014, the context of their history and future prospects.

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Section: Datamentioning

confidence: 99%

Five decades of radioglaciology

et al. 2020

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“…Such an assessment of accuracy becomes relevant when comparing the results of two surveys of the same area to determine changes in ice thickness over time (Davies and others, 2018) but is not relevant to geomorphological studies of, for example, bedform shape and size (Spagnolo and others, 2017). This is because the thickness of ice above the bedforms is of secondary importance compared to the peak-to-trough height of individual drumlins or megascale glacial lineations.…”

Section: Accuracymentioning

confidence: 99%

The precision of radar-derived subglacial bed topography: a case study from Pine Island Glacier, Antarctica

King

2020

Ann. Glaciol.

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Recent advances in the measurement of bedforms beneath active ice streams have been made using ground-based grid profiling using impulse radar systems operating with centre frequencies in the 3–5 MHz range. Surveys of Rutford Ice Stream and Pine Island Glacier have shown that features such as mega-scale glacial lineations with topographic relief of as little as 3 m can be traced for many kilometres downstream under more than 2 km of fast-moving ice. In the discussion of these data, it is often asked ‘How is it possible to map such fine-scale topography with such a low-frequency radar’. In answering that question, the key point is the distinction between the precision of a radar range measurement to a single, isolated reflective interface and the ability to resolve the presence of two closely-spaced interfaces of similar reflectivity (commonly referred to as the vertical resolution). This paper will discuss and illustrate this distinction and use the case study of data acquired over Pine Island Glacier to examine the limits of precision of the radar range measurement.

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“…If the bed beneath Thwaites Glacier is changing rapidly, as observed at Rutford Ice Stream (Smith et al, 2007) then the surface may not represent the current bed, but some long term average. However, observations at Pine Island Glacier (Brisbourne et al, 2017;Davies et al, 2018) suggest that the bed is not changing rapidly there, and it is possible that neighbouring Thwaites Glacier might be behaving similarly. Additionally, the erosion observed at Rutford Ice Stream does not significantly change the shape of the topography on the wavelengths resolved by this inversion.…”

Section: Comparison To Radar Datamentioning

confidence: 99%

Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier

Ockenden

Bingham

Curtis

et al. 2021

Preprint

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Abstract. There is significant uncertainty over how ice sheets and glaciers will respond to rising global temperatures. Limited knowledge of the topography and rheology of ice-bed interface is a key cause of this uncertainty, as models show that small changes in the bed can have a large influence on predicted rates of ice loss. Most of our detailed knowledge of bed topography comes from airborne and ground-penetrating radar observations. However, these direct observations are not spaced closely enough to meet the requirements of ice-sheet models, so interpolation and inversion methods are used to fill in the gaps. Here we present the results of a new inversion of surface-elevation and velocity data over Thwaites Glacier, West Antarctica, for bed topography and slipperiness (i.e. the degree of basal slip for a given level of drag). The inversion is based on a steady-state linear perturbation analysis of the shallow-ice-stream equations. The method works by identifying disturbances to surface flow which are caused by obstacles or sticky patches in the bed, and can therefore be applied wherever the shallow-ice-stream equations hold and where surface data are available, even where the ice thickness is not well known. We assess the performance of the inversion for topography with the available radar data. Although the topographic output from the inversion is less successful where the bed slopes steeply, it compares well with radar data from the central trunk of the glacier. This method could therefore be useful as either an independent test of other interpolation methods such as mass conservation and kriging, or as a complementary technique in regions where those techniques fail. We do not have data to allow us to assess the success of the slipperiness results from our inversions, but we provide maps that may guide future seismic data collection across Thwaites Glacier. The methods presented here show significant promise for using high-resolution satellite datasets, calibrated by the sparser field datasets, to generate high resolution bed topography products across the ice sheets, and therefore contribute to reduced uncertainty in predictions of future sea-level rise.

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How dynamic are ice-stream beds?

Cited by 13 publications

References 104 publications

Five decades of radioglaciology

Five decades of radioglaciology

The precision of radar-derived subglacial bed topography: a case study from Pine Island Glacier, Antarctica

Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier

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