Brief  Communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica

Hoffman, Andrew O.; Christianson, Knut; Shapero, Daniel; Smith, B. E.; Joughin, Ian

doi:10.5194/tc-2020-80

Cited by 9 publications

(16 citation statements)

References 21 publications

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“…After sufficient build-up, the pressure then abruptly changes in a way that facilitates more downstream transport of water to a different low in the hydraulic potential where this process is then reiterated (Figures 3b and 3c). These observations are in line with previous modeling based assertions (Dow et al, 2018) and observational studies at Recovery (Fricker et al, 2014) and Thwaites Glacier (Hoffman et al, 2020;Smith et al, 2017).…”

Section: Discussionsupporting

confidence: 92%

“…Most observations of ice‐surface uplift and subsidence are derived from satellite altimetry (e.g., Fricker et al., 2007; Siegfried & Fricker, 2018, 2021; Wingham et al., 2006), while a few studies also use Synthetic Aperture Radar (SAR) interferometry (e.g., Gray et al., 2005; Milillo et al., 2017) and SAR speckle tracking (e.g., Hoffman et al., 2020; Joughin et al., 2016). Subglacial lakes detected with these methods are often referred to as active lakes, in contrast to lakes solely detected using radio‐echo sounding (RES), which may or may not show temporal variations at the ice surface (Ashmore & Bingham, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel‐1 and ICESat‐2 Measurements

Neckel

Franke

Helm

et al. 2021

Geophysical Research Letters

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Large quantities of basal meltwater are transported from the interior of the Antarctic Ice Sheet to downstream areas of faster ice flow, reducing the frictional resistance at the glacier bed (Joughin et al., 2004;Siegfried & Fricker, 2018). Subglacial water is known to pool in subglacial lakes and can be routed hundreds of kilometers along well-defined pathways (Fricker et al., 2014;Wingham et al., 2006). Indirect evidence of subglacial water movement was first detected by analyzing localized surface elevation changes of mountain glaciers (

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel‐1 and ICESat‐2 Measurements

Neckel

Franke

Helm

et al. 2021

Geophysical Research Letters

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“…The static drag budget associated with the ridge surrounding the largest subglacial Thwaites lake (hashed region Figure 1, Thw 124 ) provides much of the resistance we observe in static inversions for basal shear stress. This may also explain why local ice dynamics are relatively insensitive to changes in effective pressure inferred from satellite altimetry time series of the lake fill‐drain cycle (Hoffman et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…The surface elevation used in the model was derived from the spatiotemporal least squares fitting procedure described by Smith et al. (2017) applied to Cryosat‐2 radar altimetry, optical satellite stereo‐imagery, and IceBridge airborne laser altimetry from the first quarter of 2016 when subglacial lakes beneath Thwaites Glacier were inactive (Hoffman et al., 2020).…”

Section: Methodsmentioning

confidence: 99%

The Impact of Basal Roughness on Inland Thwaites Glacier Sliding

Hoffman

Christianson

Holschuh

et al. 2022

Geophysical Research Letters

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Swath radar technology enables three‐dimensional mapping of modern glacier beds over large areas at resolutions that are higher than those typically used in ice‐flow models. These data may enable new understanding of processes at the ice‐bed interface. Here, we use two densely surveyed swath‐mapped topographies (<50 m2 resolution) of Thwaites Glacier to investigate the sensitivity of inferred basal friction proxies to bed roughness magnitude and orientation. Our work suggests that along‐flow roughness influences inferred friction more than transverse‐flow roughness, which agrees with analytic form‐drag sliding theory. Using our model results, we calculate the slip length (the ratio of internal shear to basal slip). We find excellent agreement between the numerically derived slip lengths and slip lengths predicted by analytic form‐drag sliding theory, which suggests that unresolved short wavelength bed roughness may control sliding in the Thwaites interior.

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“…In contrast, geostatistical simulation provides a framework for quantifying hydrological uncertainty with respect to topographic uncertainty. Some of the modelled tributaries are located over a system of active subglacial lakes -lakes at the ice-bed interface that periodically drain and refill (Hoffman et al, 2020;Smith et al, 2017). These lakes are hypothesized to be hydrologically connected, with a drain and refill cycle that depends on the level of connectivity (Malczyk et al, 2020;Smith et al, 2017).…”

Section: Uncertainty In Subglacial Hydrological Flowmentioning

confidence: 99%

Mapping high-resolution basal topography of West Antarctica from radar data using non-stationary multiple-point geostatistics (MPS-BedMappingV1)

et al. 2022

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Abstract. The subglacial bed topography is critical for modelling the evolution of Thwaites Glacier in the Amundsen Sea Embayment (ASE), where rapid ice loss threatens the stability of the West Antarctic Ice Sheet. However, mapping of subglacial topography is subject to uncertainties of up to hundreds of metres, primarily due to large gaps of up to tens of kilometres in airborne ice-penetrating radar flight lines. Deterministic interpolation approaches do not reflect such spatial uncertainty. While traditional geostatistical simulations can model such uncertainty, they become difficult to apply because of the significant non-stationary spatial variation of topography over such large surface area. In this study, we develop a non-stationary multiple-point geostatistical (MPS) approach to interpolate large areas with irregular geophysical data and apply it to model the spatial uncertainty of entire ASE basal topography. We collect 166 high-quality topographic training images (TIs) of resolution 500 m to train the gap-filling of radar data gaps, thereby simulating realistic topography maps. The TIs are extensively sampled from deglaciated regions in the Arctic as well as Antarctica. To address the non-stationarity in topographic modelling, we introduce a Bayesian framework that models the posterior distribution of non-stationary TIs assigned to the local line data. Sampling from this distribution then provides candidate training images for local topographic modelling with uncertainty, constrained to radar flight line data. Compared to traditional MPS approaches that do not consider uncertain TI sampling, our approach results in a significant improvement in the topographic modelling quality and efficiency of the simulation algorithm. Finally, we simulate multiple realizations of high-resolution ASE topographic maps. We use the multiple realizations to investigate the impact of basal topography uncertainty on subglacial hydrological flow patterns.

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Brief Communication: Heterogenous thinning and subglacial lake activity on Thwaites Glacier, West Antarctica

Cited by 9 publications

References 21 publications

Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel‐1 and ICESat‐2 Measurements

Evidence of Cascading Subglacial Water Flow at Jutulstraumen Glacier (Antarctica) Derived From Sentinel‐1 and ICESat‐2 Measurements

The Impact of Basal Roughness on Inland Thwaites Glacier Sliding

Mapping high-resolution basal topography of West Antarctica from radar data using non-stationary multiple-point geostatistics (MPS-BedMappingV1)

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