Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment

Lhermitte, Stef; Sun, Sainan; Shuman, Christopher A.; Wouters, Bert; Pattyn, Frank; Wuite, Jan; Berthier, Étienne; Nägler, Thomas

doi:10.1073/pnas.1912890117

Cited by 137 publications

(172 citation statements)

References 56 publications

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“…For the northern GVIIS, we also derive smaller-scale melt information from an enhanced resolution C-band (5.225 GHz) VV polarization radar backscatter image time series collected by EUMETSAT's Advanced SCATterometer (AS-CAT), aboard the tandem polar-orbiting satellites MetOp-A and MetOp-B. The 4.45 km enhanced product is obtained by applying the Scatterometer Image Reconstruction (SIR) algorithm with filtering (Lindsley and Long, 2016), which is used to improve the spatial resolution of irregularly and oversampled data (Early and Long, 2001). The effective spatial resolution was estimated at ∼ 12-15 km, three-fold finer than the effective resolution of the SMMR/SSMI-based product (∼ 50 km).…”

Section: Small-scale Microwave Scatterometer Observations Of Meltmentioning

confidence: 99%

The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula

et al. 2021

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Abstract. In the 2019/2020 austral summer, the surface melt duration and extent on the northern George VI Ice Shelf (GVIIS) was exceptional compared to the 31 previous summers of distinctly lower melt. This finding is based on analysis of near-continuous 41-year satellite microwave radiometer and scatterometer data, which are sensitive to meltwater on the ice shelf surface and in the near-surface snow. Using optical satellite imagery from Landsat 8 (2013 to 2020) and Sentinel-2 (2017 to 2020), record volumes of surface meltwater ponding were also observed on the northern GVIIS in 2019/2020, with 23 % of the surface area covered by 0.62 km3 of ponded meltwater on 19 January. These exceptional melt and surface ponding conditions in 2019/2020 were driven by sustained air temperatures ≥0 ∘C for anomalously long periods (55 to 90 h) from late November onwards, which limited meltwater refreezing. The sustained warm periods were likely driven by warm, low-speed (≤7.5 m s−1) northwesterly and northeasterly winds and not by foehn wind conditions, which were only present for 9 h total in the 2019/2020 melt season. Increased surface ponding on ice shelves may threaten their stability through increased potential for hydrofracture initiation; a risk that may increase due to firn air content depletion in response to near-surface melting.

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Section: Small-scale Microwave Scatterometer Observations Of Meltmentioning

confidence: 99%

The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula

et al. 2021

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“…The open source ice flow model Úa (Gudmundsson, 2020) uses the finite-element method to solve the shallow ice stream equations, commonly referred to as SSA or SSTREAM (Hutter, 1983;MacAyeal, 1989), on an irregular triangular mesh. The diagnostic velocity solver is based on an iterative Newton-Raphson method.…”

Section: Appendix B: Model Configuration and Optimizationmentioning

confidence: 99%

Drivers of Pine Island Glacier speed-up between 1996 and 2016

et al. 2021

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Abstract. Pine Island Glacier in West Antarctica is among the fastest changing glaciers worldwide. Over the last 2 decades, the glacier has lost in excess of a trillion tons of ice, or the equivalent of 3 mm of sea level rise. The ongoing changes are thought to have been triggered by ocean-induced thinning of its floating ice shelf, grounding line retreat, and the associated reduction in buttressing forces. However, other drivers of change, such as large-scale calving and changes in ice rheology and basal slipperiness, could play a vital, yet unquantified, role in controlling the ongoing and future evolution of the glacier. In addition, recent studies have shown that mechanical properties of the bed are key to explaining the observed speed-up. Here we used a combination of the latest remote sensing datasets between 1996 and 2016, data assimilation tools, and numerical perturbation experiments to quantify the relative importance of all processes in driving the recent changes in Pine Island Glacier dynamics. We show that (1) calving and ice shelf thinning have caused a comparable reduction in ice shelf buttressing over the past 2 decades; that (2) simulated changes in ice flow over a viscously deforming bed are only compatible with observations if large and widespread changes in ice viscosity and/or basal slipperiness are taken into account; and that (3) a spatially varying, predominantly plastic bed rheology can closely reproduce observed changes in flow without marked variations in ice-internal and basal properties. Our results demonstrate that, in addition to its evolving ice thickness, calving processes and a heterogeneous bed rheology play a key role in the contemporary evolution of Pine Island Glacier.

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“…Extensive surface ponding (Arthur et al 2020;Dell et al, 2020;Kingslake et al, 2017) may threaten ice-shelf stability due to stress variations associated with meltwater movement, ponding and drainage (Scambos et al, 2000(Scambos et al, , 2003MacAyeal et al, 2003;Banwell and MacAyeal, 2015;Banwell et al 2019). These processes may initiate meltwater-induced vertical fracturing ('hydrofracturing') (Van der Veen, 2007;Dunmire et al, 2020;Lai et al 2020), especially if the ice shelf is already damaged with a high density of crevasses (Lhermitte et al, 2020). The collapse of the Larsen B ice shelf in 2002 is arguably the most famous break-up event due to its rapidity and extent (e.g.…”

mentioning

confidence: 99%

32-year record-high surface melt in 2019/2020 on north George VI Ice Shelf, Antarctic Peninsula

Banwell¹,

Datta²,

Dell³

et al. 2020

Preprint

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Abstract. In the 2019/2020 austral summer, the surface melt duration and extent on the northern George VI Ice Shelf (GVIIS) was exceptional compared to the 31 previous summers of dramatically lower melt. This finding is based on analysis of near-continuous 41-year satellite microwave radiometer (and scatterometer) data, which are sensitive to meltwater on the ice-shelf surface and in the near-surface snow. Using optical satellite imagery from Landsat 8 (since 2013) and Sentinel-2 (since 2017), record volumes of surface meltwater ponding are also observed on north GVIIS in 2019/2020, with 23 % of the surface area covered by 0.62 km3 of meltwater on January 19. These exceptional melt and surface ponding conditions in 2019/2020 were driven by sustained air temperatures ≥ 0 °C for anomalously long periods (55–90 hours) from late November onwards, likely driven by warmer northwesterly and northeasterly low-speed winds. Increased surface ponding on ice shelves may threaten their stability through increased potential for hydrofracture initiation; a risk that may increase due to firn air content depletion in response to near-surface melting.

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Damage accelerates ice shelf instability and mass loss in Amundsen Sea Embayment

Cited by 137 publications

References 56 publications

The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula

The 32-year record-high surface melt in 2019/2020 on the northern George VI Ice Shelf, Antarctic Peninsula

Drivers of Pine Island Glacier speed-up between 1996 and 2016

32-year record-high surface melt in 2019/2020 on north George VI Ice Shelf, Antarctic Peninsula

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