Impact of Iceberg Calving on the Retreat of Thwaites Glacier, West Antarctica Over the Next Century With Different Calving Laws and Ocean Thermal Forcing

Yu, Hongju; Rignot, Eric; Seroussi, H. L.; Morlighem, Mathieu; Choi, Youngmin

doi:10.1029/2019gl084066

Cited by 17 publications

(16 citation statements)

References 65 publications

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“…Some glaciers in the Amundsen Sea Embayment are already close to this threshold and experiencing substantial grounding line retreat ( 9 ). The grounding line of Thwaites glacier is only ~30 km away from the subglacial ridge and retreating at ~1 km per year ( 47 ); eventual collapse may already be inevitable ( 10 , 45 ). Models support irreversible retreat being underway for present levels of ocean warming ( 25 , 48 ) and suggest that losing Thwaites glacier may destabilize much of WAIS ( 7 ).…”

Section: The Climate Tipping Elementsmentioning

confidence: 99%

Exceeding 1.5°C global warming could trigger multiple climate tipping points

McKay

Staal

Abrams

et al. 2022

Science

993

345

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Climate tipping points occur when change in a part of the climate system becomes self-perpetuating beyond a warming threshold, leading to substantial Earth system impacts. Synthesizing paleoclimate, observational, and model-based studies, we provide a revised shortlist of global “core” tipping elements and regional “impact” tipping elements and their temperature thresholds. Current global warming of ~1.1°C above preindustrial temperatures already lies within the lower end of some tipping point uncertainty ranges. Several tipping points may be triggered in the Paris Agreement range of 1.5 to <2°C global warming, with many more likely at the 2 to 3°C of warming expected on current policy trajectories. This strengthens the evidence base for urgent action to mitigate climate change and to develop improved tipping point risk assessment, early warning capability, and adaptation strategies.

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Section: The Climate Tipping Elementsmentioning

confidence: 99%

Exceeding 1.5°C global warming could trigger multiple climate tipping points

McKay

Staal

Abrams

et al. 2022

Science

993

345

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“… Thwaites Glacier is one of the fastest-changing ice–ocean systems in Antarctica 1 – 3 . Much of the ice sheet within the catchment of Thwaites Glacier is grounded below sea level on bedrock that deepens inland 4 , making it susceptible to rapid and irreversible ice loss that could raise the global sea level by more than half a metre 2 , 3 , 5 . The rate and extent of ice loss, and whether it proceeds irreversibly, are set by the ocean conditions and basal melting within the grounding-zone region where Thwaites Glacier first goes afloat 3 , 6 , both of which are largely unknown.…”

mentioning

confidence: 99%

Suppressed basal melting in the eastern Thwaites Glacier grounding zone

Davis

Nicholls

Holland

et al. 2023

Nature

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Thwaites Glacier is one of the fastest-changing ice–ocean systems in Antarctica1–3. Much of the ice sheet within the catchment of Thwaites Glacier is grounded below sea level on bedrock that deepens inland4, making it susceptible to rapid and irreversible ice loss that could raise the global sea level by more than half a metre2,3,5. The rate and extent of ice loss, and whether it proceeds irreversibly, are set by the ocean conditions and basal melting within the grounding-zone region where Thwaites Glacier first goes afloat3,6, both of which are largely unknown. Here we show—using observations from a hot-water-drilled access hole—that the grounding zone of Thwaites Eastern Ice Shelf (TEIS) is characterized by a warm and highly stable water column with temperatures substantially higher than the in situ freezing point. Despite these warm conditions, low current speeds and strong density stratification in the ice–ocean boundary layer actively restrict the vertical mixing of heat towards the ice base7,8, resulting in strongly suppressed basal melting. Our results demonstrate that the canonical model of ice-shelf basal melting used to generate sea-level projections cannot reproduce observed melt rates beneath this critically important glacier, and that rapid and possibly unstable grounding-line retreat may be associated with relatively modest basal melt rates.

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“…Nonetheless, it does not mean that these ice shelves will not collapse through other mechanisms, in particular ocean-induced basal melting, as observed and projected for Thwaites (e.g. Milillo et al, 2019;Yu et al, 2019) with positive feedbacks to ice damage and ice discharge (Lhermitte et al, 2020).…”

Section: Discussionmentioning

confidence: 97%

Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet

et al. 2021

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Abstract. We present projections of West Antarctic surface mass balance (SMB) and surface melt to 2080–2100 under the RCP8.5 scenario and based on a regional model at 10 km resolution. Our projections are built by adding a CMIP5 (Coupled Model Intercomparison Project Phase 5) multi-model-mean seasonal climate-change anomaly to the present-day model boundary conditions. Using an anomaly has the advantage to reduce CMIP5 model biases, and a perfect-model test reveals that our approach captures most characteristics of future changes despite a 16 %–17 % underestimation of projected SMB and melt rates. SMB over the grounded ice sheet in the sector between Getz and Abbot increases from 336 Gt yr−1 in 1989–2009 to 455 Gt yr−1 in 2080–2100, which would reduce the global sea level changing rate by 0.33 mm yr−1. Snowfall indeed increases by 7.4 % ∘C−1 to 8.9 % ∘C−1 of near-surface warming due to increasing saturation water vapour pressure in warmer conditions, reduced sea-ice concentrations, and more marine air intrusion. Ice-shelf surface melt rates increase by an order of magnitude in the 21st century mostly due to higher downward radiation from increased humidity and to reduced albedo in the presence of melting. There is a net production of surface liquid water over eastern ice shelves (Abbot, Cosgrove, and Pine Island) but not over western ice shelves (Thwaites, Crosson, Dotson, and Getz). This is explained by the evolution of the melt-to-snowfall ratio: below a threshold of 0.60 to 0.85 in our simulations, firn air is not entirely depleted by melt water, while entire depletion and net production of surface liquid water occur for higher ratios. This suggests that western ice shelves might remain unaffected by hydrofracturing for more than a century under RCP8.5, while eastern ice shelves have a high potential for hydrofracturing before the end of this century.

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Impact of Iceberg Calving on the Retreat of Thwaites Glacier, West Antarctica Over the Next Century With Different Calving Laws and Ocean Thermal Forcing

Cited by 17 publications

References 65 publications

Exceeding 1.5°C global warming could trigger multiple climate tipping points

Exceeding 1.5°C global warming could trigger multiple climate tipping points

Suppressed basal melting in the eastern Thwaites Glacier grounding zone

Future surface mass balance and surface melt in the Amundsen sector of the West Antarctic Ice Sheet

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