The Antarctic contribution to 21st century sea-level rise predicted by the UK Earth System Model with an interactive ice sheet

Siahaan, Antony; Smith, Robin; Holland, Paul R.; Jenkins, Adrian; Gregory, Jonathan M.; Lee, Victoria; Mathiot, Pierre; Payne, Tony; Ridley, Jeff; Jones, Colin

doi:10.5194/tc-2021-371

Cited by 5 publications

(4 citation statements)

References 66 publications

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“…The Ross and Ronne-Filchner have the potential to funnel vast quantities of grounded ice into the ocean. Other modeling studies have indeed illustrated the potential for the Filchner-Ronne cavity to flip between 'cold' and 'warm' states (Hazel and Stewart, 2020;Hellmer et al, 2017;Naughten et al, 2021), causing an order of magnitude increase in sub-shelf melt rates and subsequent increases in sea level contributions (Siahaan et al, 2021). We find that EAIS mass loss also correlates better with γ 0 than p, particularly when forced by warmer AOGCMs, suggesting more sensitivity to ocean warming than ice parameters.…”

Section: Synthetic Tf Perturbations In the Amundsen Sea Sectorsupporting

confidence: 57%

“…While some modeling centers have coupled an interactive Greenland Ice Sheet with an AOGCM, only a few have even included ice shelf cavities around Antarctica yet (e.g. UKESM (Siahaan et al, 2021) and E3SM (Comeau et al, 2022)). CESM developmental code supports a coupled Antarctic ice sheet, but it has yet to be validated as of this writing.…”

Section: Synthetic Tf Perturbations In the Amundsen Sea Sectormentioning

confidence: 99%

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Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Berdahl

Leguy

Lipscomb

et al. 2022

Preprint

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Abstract. Multi-meter sea level rise (SLR) is thought to be possible within a century or two, with most of the uncertainty originating from the Antarctic land ice contribution. One source of uncertainty relates to the ice sheet model initialization. Since ice sheets have a long response time (compared to other Earth system components such as the atmosphere), ice sheet model initialization methods can have significant impacts on how the ice sheet responds to future forcings. To assess this, we generated 25 different ice sheet spin-ups, using the Community Ice Sheet Model (CISM) at 4 km resolution. During each spin-up we varied two key parameters known to impact the sensitivity of the ice sheet to future forcing: One related to the sensitivity of the ice-shelf melt rate to ocean thermal forcing, and the other related to the basal friction. The spin-ups all nudge toward observed thickness and enforce a no-advance calving criterion, such that all final spun-up states resemble observations but differ in their melt and friction parameter settings. Each spin-up was then forced with future ocean thermal forcings from 13 different CMIP6 models under the SSP5-8.5 emissions scenario, and modern climatological surface mass balance data. Our results show that the effects of the ice sheet and ocean parameter settings used during the spin-up are capable of impacting multi-century future SLR predictions by as much as 2 m. By the end of this century, the effects of these choices are more modest, but still significant, with differences of up to 0.2 m of SLR. We have identified a combined ocean and ice parameter space that leads to widespread mass loss (low friction & high melt rate sensitivity). To explore temperature thresholds, we also ran a synthetically-forced CISM ensemble that is focused on the Amundsen region only. We find that given certain ocean and ice parameter choices, Amundsen mass loss can be triggered with thermal forcing anomalies between 1.5 and 2 °C. Our results emphasize the critical importance of considering ice sheet/ocean parameter choices during spin-up for sea level rise predictions.

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Section: Synthetic Tf Perturbations In the Amundsen Sea Sectorsupporting

confidence: 57%

Section: Synthetic Tf Perturbations In the Amundsen Sea Sectormentioning

confidence: 99%

Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Berdahl

Leguy

Lipscomb

et al. 2022

Preprint

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“…A second model variant UKESM1.0-ice has generated climate projections with an active Antarctic Ice Sheet model (Siahaan et al, 2021). However, UKESM1.0-ice has not been used to produce the historical (1850-2014) period because the ice sheet model needs to be initialized in the present day (Siahaan et al, 2021). An analysis of the historical RG evolution is a key feature of our study, and so we focus solely on UKESM1 simulations.…”

Section: Methodsmentioning

confidence: 99%

Projected West Antarctic Ocean Warming Caused by an Expansion of the Ross Gyre

Gómez-Valdivia

Holland

Siahaan

et al. 2023

Geophysical Research Letters

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The cyclonic Ross Gyre (RG) occupies the south-west Pacific sector of the Southern Ocean (Figure 1a). Evidence from hydrographic data (Gouretski, 1999), satellite altimetry (Dotto et al., 2018), and modeling (Rickard et al., 2010) suggests the RG extends more than 3,000 m below the ocean surface, with a transport of ∼20 Sv, dominating the large-scale thermohaline structure of the Ross Sea (RS). The horizontal RG extent is limited by the continental shelf break to the south and the Pacific-Antarctic Ridge (PAR) to the north and west (Figure 1a). The southward-flowing eastern limb of the RG is much less strongly constrained by topography (Patmore et al., 2019) and its location is more variable (Dotto et al., 2018;Sokolov & Rintoul, 2009). The eastern RG limb, and the adjacent Antarctic Circumpolar Current (ACC), supply warm Circumpolar Deep Water (CDW) to the Amundsen Sea (AS) shelf (Jenkins et al., 2016;Nakayama et al., 2018) that supports rapid melting when it reaches ice shelf cavities. Increases in such ocean-driven melting are known to be causing thinning of the ice sheet in the nearby Amundsen-Bellingshausen Seas (Depoorter et al., 2013;Jenkins et al., 2016).Satellite altimetry reveals variability in the RG strength and the eastern RG boundary position (Armitage et al., 2018;Dotto et al., 2018;Sokolov & Rintoul, 2009); whereas, numerical experiments have shown that the RG variability influences the water masses along the AS shelf (Nakayama et al., 2018). Any changes in the circulation of this region may be of wide importance, considering the ocean-driven ice loss from West Antarctica during recent decades (Paolo et al., 2015) and the consequences for global sea-level rise (Shepherd et al., 2018).We use numerical simulations of the United Kingdom Earth System Model (UKESM1) implementation for the Coupled Model Intercomparison Project 6 (CMIP6) (Sellar et al., 2020) to analyze the RG dynamics and its effects on the Amundsen and Bellingshausen seas. We consider historical simulations and two contrasting future climate scenarios associated with the Shared Socioeconomic Pathways SSP1-1.9 and SSP5-8.5 (Riahi et al., 2017).

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“…Solid Earthśice sheetśoceanśclimate interactions on many time scales [39] are a signiőcant challenge for ice sheet simulations. Climate, ocean and sea-level forcings in uncoupled ice sheet models are themselves dependent on the simulated ice sheet response, yet the high computational cost of coupled models currently limits experiments to short time periods or coarse spatial resolution [80,93,107,118]. For currently available computer resources, glacial cycle simulations with adequate representation of grounding line and ice stream dynamics still require uncoupled ice sheet models.…”

Section: Methodsmentioning

confidence: 99%

Antarctic Ice Sheet tipping in the last 800 kyr warns of future ice loss

Langebroek

Reese

Albrecht

et al. 2023

Preprint

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Ice loss from Antarctica's vast freshwater reservoir could threaten coastal communities and the global economy if the ice volume decreases by even just a few percent [1]. Key processes controlling the fine balance between ice gain and ice loss remain poorly constrained, so that Antarctica's contribution to future sea-level changes ranks as the most uncertain of all potential contributors [2]. Meanwhile, observed changes in mass balance are limited to ~40 years [3,4] and difficult to put into context for an ice sheet with response time scales reaching centuries to millennia. To gain a much longer-term perspective, we here combine transient and equilibrium Parallel Ice Sheet Model [5,6] simulations of Antarctic Ice Sheet response to repeated glacial-interglacial warming and cooling cycles over the last 800,000 years. We find hysteresis (path-dependent states [7,8]) in the ice sheet response that is caused both by the long response time and by crossing of tipping points [9]. Notably, West Antarctic Ice Sheet collapse contributes over 4 m sea-level rise in all equilibrium ice sheet states with ocean temperatures only 0 to 0.25°C warmer than present. A “borrowed time” (overshoot) scenario best characterises our present-day ice sheet, supporting recent studies warning of substantial irreversible ice loss on millennial time-scales, even without further climate warming [10-12].

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The Antarctic contribution to 21st century sea-level rise predicted by the UK Earth System Model with an interactive ice sheet

Cited by 5 publications

References 66 publications

Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Exploring ice sheet model sensitivity to ocean thermal forcing using the Community Ice Sheet Model (CISM)

Projected West Antarctic Ocean Warming Caused by an Expansion of the Ross Gyre

Antarctic Ice Sheet tipping in the last 800 kyr warns of future ice loss

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