The sensitivity of West Antarctica to the submarine melting feedback

Arthern, Robert; Williams, C.

doi:10.1002/2017gl072514

Cited by 79 publications

(123 citation statements)

References 54 publications

(106 reference statements)

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“…The lack of grounding line retreat (which would lead to additional VAF loss) may be because the nature of the experiments precludes melt under newly floating ice; other modeling studies (Arthern & Williams, 2017;Seroussi et al, 2017) suggest that melting of newly exposed shelf near the grounding line has a large impact on retreat. Still, the additional mass loss, ∼3 km 3 /a, is not large relative to the ∼21 km 3 /a currently being lost from the region.…”

Section: Discussionmentioning

confidence: 98%

How Accurately Should We Model Ice Shelf Melt Rates?

Goldberg

Gourmelen

Kimura

et al. 2019

Geophysical Research Letters

127

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Assessment of ocean‐forced ice sheet loss requires that ocean models be able to represent sub‐ice shelf melt rates. However, spatial accuracy of modeled melt is not well investigated, and neither is the level of accuracy required to assess ice sheet loss. Focusing on a fast‐thinning region of West Antarctica, we calculate spatially resolved ice‐shelf melt from satellite altimetry and compare against results from an ocean model with varying representations of cavity geometry and ocean physics. Then, we use an ice‐flow model to assess the impact of the results on grounded ice. We find that a number of factors influence model‐data agreement of melt rates, with bathymetry being the leading factor; but this agreement is only important in isolated regions under the ice shelves, such as shear margins and grounding lines. To improve ice sheet forecasts, both modeling and observations of ice‐ocean interactions must be improved in these critical regions.

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Section: Discussionmentioning

confidence: 98%

How Accurately Should We Model Ice Shelf Melt Rates?

Goldberg

Gourmelen

Kimura

et al. 2019

Geophysical Research Letters

127

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“…Numerous modeling studies have demonstrated that ice shelf basal melting is a critical factor in driving ice sheet retreat (e.g. Arthern & Williams, ; Cornford et al, ; DeConto & Pollard, ; Favier et al, ; Goldberg et al, ; Joughin et al, ), with basal melting near the grounding zone and in the new sub‐ice shelf cavities created as melting ice shelves go afloat being particularly important (Arthern & Williams, ; Reese et al, ; R. T. Walker et al, ). Thus, realistic representations of the magnitude and distribution of ice shelf basal melting in global climate models is essential for forecasting 21st century sea level rise.…”

Section: Introductionmentioning

confidence: 99%

“…Numerous modeling studies have demonstrated that ice shelf basal melting is a critical factor in driving ice sheet retreat (e.g. Arthern & Williams, 2017;Cornford et al, 2015;DeConto & Pollard, 2016;Favier et al, 2014;Goldberg et al, 2019;Joughin et al, 2014), with basal melting near the grounding zone and in the new sub-ice shelf cavities created as melting ice shelves go afloat being particularly important (Arthern & Williams, 2017;Reese et al, 2018;R. T. Walker et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Turbulence Observations Beneath Larsen C Ice Shelf, Antarctica

Davis

Nicholls

2019

JGR Oceans

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Increased ocean‐driven basal melting beneath Antarctic ice shelves causes grounded ice to flow into the ocean at an accelerated rate, with consequences for global sea level. The turbulent transfer of heat through the ice shelf‐ocean boundary layer is critical in setting the basal melt rate, yet the processes controlling this transfer are poorly understood and inadequately represented in global climate models. This creates large uncertainties in predictions of future sea level rise. Using a hot‐water drilled access hole, two turbulence instrument clusters (TICs) were deployed 2.5 and 13.5 m beneath Larsen C ice shelf in December 2011. Both instruments returned a yearlong record of turbulent velocity fluctuations, providing a unique opportunity to explore the turbulent processes within the ice shelf‐ocean boundary layer. Although the scaling between the turbulent kinetic energy (TKE) dissipation rate and mean flow speed varies with distance from the ice shelf base, at both TICs the TKE dissipation rate is balanced entirely by the rate of shear production. The freshwater released by basal melting plays no role in the TKE balance. When the upper TIC is within the log‐layer, we derive an under‐ice drag coefficient of 0.0022 and a roughness length of 0.44 mm, indicating that the ice base is smooth. Finally, we demonstrate that although the canonical three‐equation melt rate parameterization can accurately predict the melt rate for this example of smooth ice underlain by a cold, tidally forced boundary layer, the law of the wall assumption employed by the parameterization does not hold at low flow speeds.

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“…We chose to use a model domain that follows the present‐day boundaries of Thwaites Glacier to keep model cost low enough to allow simulation of many ensemble members. However, previous studies have shown that the boundaries of Thwaites Glacier are likely to expand significantly in the future due to interactions with neighboring basins, particularly Pine Island Glacier (Arthern & Williams, ; Cornford et al, ). While ignoring this effect will affect the projections of total mass loss from the model, we expect it to have a secondary effect on quantifying the impacts of including or excluding ocean variability.…”

Section: Comparison To Other Studies Of Ice‐sheet Response To Climatementioning

confidence: 99%

Effect of Subshelf Melt Variability on Sea Level Rise Contribution From Thwaites Glacier, Antarctica

et al. 2019

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Modeling and observations suggest that Thwaites Glacier, West Antarctica, has begun unstable retreat. Concurrently, oceanographic observations have revealed substantial multiyear variability in the temperature of the ocean water driving retreat through melting of the ice shelf that restrains inland glacier flow. Using an ensemble of 72 ice‐sheet model simulations that include an idealized representation of ocean temperature variability, we find that variable ice‐shelf melting causes delays in grounding line retreat, mass loss, and sea level contribution relative to steady forcing. Modeled delays are up to 43 years after 500 years of simulation, corresponding to a 10% reduction in glacier mass loss. Delays are primarily caused by asymmetric melt forcing in the presence of variability. For the “warm cavity” conditions beneath Thwaites Ice Shelf, increases in access of warm, deeper water are unable to raise water temperatures in the cavity by much, whereas increases in access of significantly colder, shallow water reduce cavity water temperatures substantially. This leads to lowered mean melt rates under variable ocean temperature forcing. Additionally, about one quarter of the mass loss delay is caused by a nonlinear ice dynamic response to varying ice‐shelf thinning rate, which is amplified during the initial phases of unstable, bed‐topography‐driven retreat. Mass loss rates under variability differ by up to 50% from ensemble mean values at any given time. Our results underscore the need for taking climate variability into account when modeling ice sheet evolution and for continued efforts toward the coupling of ice sheet models to ocean and climate models.

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The sensitivity of West Antarctica to the submarine melting feedback

Cited by 79 publications

References 54 publications

How Accurately Should We Model Ice Shelf Melt Rates?

How Accurately Should We Model Ice Shelf Melt Rates?

Turbulence Observations Beneath Larsen C Ice Shelf, Antarctica

Effect of Subshelf Melt Variability on Sea Level Rise Contribution From Thwaites Glacier, Antarctica

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