Scaling of instability timescales of Antarctic outlet glaciers based on one-dimensional similitude analysis

Levermann, Anders; Feldmann, Johannes

doi:10.5194/tc-13-1621-2019

Cited by 8 publications

(15 citation statements)

References 67 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This is clearly replicated in all three ice flow models. Alongside this, Pine Island and Thwaites glaciers have fast response timescales, consistent with the results of Levermann and Feldmann (2019). This reversibility is evident even under the strongest perturbation in which a number of the smaller ice shelves disappear entirely during the perturbation period.…”

Section: Discussionsupporting

confidence: 88%

The stability of present-day Antarctic grounding lines – Part A: No indication of marine ice sheet instability in the current geometry

Urruty

Hill

Reese

et al. 2022

Preprint

View full text Add to dashboard Cite

Abstract. Theoretical and numerical work has firmly established that grounding lines of marine-type ice sheets can enter phases of irreversible advance and retreat driven by the marine ice sheet instability (MISI). Instances of such irreversible retreat have been found in several simulations of the past and future evolution of the Antarctic Ice Sheet. However, hitherto the stability regime of Antarctic Ice Sheet grounding lines in their current position has not been assessed. Here we conduct a systematic numerical stability analysis of all the grounding lines of the Antarctic Ice Sheet to determine if they are currently undergoing irreversible retreat through MISI. To do this, we initialise three state-of-the-art ice-flow models, Úa, Elmer/Ice, and PISM, to replicate the current geometry of the Antarctic Ice Sheet, and then apply small, but numerically significant, perturbations in ocean-induced ice-shelf melt. We find that the grounding lines around Antarctica migrate slightly away from their initial position while the perturbation is applied, and then revert to the initial state once the perturbation is removed. There is no indication of irreversible or self-sustaining retreat. This suggests that present-day grounding-line retreat is driven by external climate forcing alone. Hence, if the currently observed mass imbalance were to be removed, the grounding-line retreat would likely stop. However, under present-day climate forcing, further grounding-line retreat is expected, and our accompanying paper (Part B, Reese et al., 2022) shows that this could eventually lead to a collapse of some marine regions of West Antarctica.

show abstract

Section: Discussionsupporting

confidence: 88%

The stability of present-day Antarctic grounding lines – Part A: No indication of marine ice sheet instability in the current geometry

Urruty

Hill

Reese

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…1.0°C to 1.5°C above the pre-industrial global average surface air temperature level. These include progressive thawing of permafrost soils [386], melting of Greenland ice [387], Western Antarctic Ice Shield instability [388], and coral reef dieback [4]. This would mean that for a higher level of climate security, substantially more ambitious climate targets must be the target.…”

Section: Progressing 100% Renewable Energy Systems Research Towards N...mentioning

confidence: 99%

On the History and Future of 100% Renewable Energy Systems Research

et al. 2022

View full text Add to dashboard Cite

Research on 100% renewable energy systems is a relatively recent phenomenon. It was initiated in the mid-1970s, catalyzed by skyrocketing oil prices. Since the mid-2000s, it has quickly evolved into a prominent research field encompassing an expansive and growing number of research groups and organizations across the world. The main conclusion of most of these studies is that 100% renewables is feasible worldwide at low cost. Advanced concepts and methods now enable the field to chart realistic as well as cost-or resource-optimized and efficient transition pathways to a future without the use of fossil fuels. Such proposed pathways in turn, have helped spur 100% renewable energy policy targets and actions, leading to more research. In most transition pathways, solar energy and wind power increasingly emerge as the central pillars of a sustainable energy system combined with energy efficiency measures. Costoptimization modeling and greater resource availability tend to lead to higher solar photovoltaic shares, while emphasis on energy supply diversification tends to point to higher wind power contributions. Recent research has focused on the challenges and opportunities regarding grid congestion, energy storage, sector coupling, electrification of transport and industry implying power-to-X and hydrogen-to-X, and the inclusion of natural and technical carbon dioxide removal (CDR) approaches. The result is a holistic vision of the transition towards a net-negative greenhouse gas emissions economy that can limit global warming to 1.5˚C with a clearly defined carbon budget in a sustainable and cost-effective manner based on 100% renewable energy-industry-CDR systems. Initially, the field encountered very strong skepticism. Therefore, this paper also includes a response to major critiques against 100% renewable energy systems, and also discusses the institutional inertia that hampers adoption by the International Energy Agency and the Intergovernmental Panel on Climate Change, as well as possible negative connections to community acceptance and energy justice. We conclude by discussing how this emergent research field can further progress to the benefit of society.

show abstract

“…In fact, the timescale of TG estimated here is about ten times faster than in the previous study, since the present study takes into account the much larger width of TG (and thus the smaller buttressing effect of its grounded portion) compared to the reference PIG. In contrast, in the present study basal stresses are neglected, whereas in Levermann and Feldmann (2019) there is a separate scaling law that involves basal friction parameter.…”

Section: Discussionmentioning

confidence: 82%

“…The quantitative influence of buttressing on the timescales of confined ice flow and the related discharge in general as well as on MISI timescales in particular require detailed numerical computations (Favier et al, 2014;Joughin et al, 2014;Pattyn and Morlighem, 2020). By comparing similar ice dynamics it is however possible to derive scaling relations that comprise the complex stress and velocity field without the need of computationally expensive simulations (Feldmann and Levermann, 2016;Levermann and Feldmann, 2019). Such relations provide a link between the characteristic scales of a glacier, e.g., between its ice-flow timescale and its geometric dimensions.…”

Section: Introductionmentioning

confidence: 99%

“…In Sect. 4 we apply the scaling relation to a set of MISI-prone Antarctic outlet glaciers to compare their timescales, using a method that is principally similar to but more sophisticated than the one used in Levermann and Feldmann (2019) as we here extend it to both horizontal dimensions and carry out a more profound statistical analysis of the obtained outlet-specific scales. The limitations of our approach are discussed in Sect.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Timescales of outlet-glacier flow with negligible basal friction: Theory, observations and modeling

Feldmann

Levermann

2022

Preprint

Self Cite

View full text Add to dashboard Cite

Abstract. The timescales of the flow and retreat of Greenland's and Antarctica's outlet glaciers and their potential instabilities are arguably the largest uncertainty in future sea-level projections. Here we derive a scaling relation that allows the comparison of the timescales of observed complex ice flow fields with geometric similarity. The scaling relation is derived under the assumption of fast, laterally confined, geometrically similar outlet-glacier flow over a slippery bed, i.e., with negligible basal friction. According to the relation, the time scaling of the outlet flow is determined by the product of the inverse of 1) the fourth power of the width-to-length ratio of its confinement, 2) the third power of the confinement depth and 3) the temperature-dependent ice softness. For the outflow at the grounding line of streams with negligible basal friction this means that the volume flux is proportional to the ice temperature and the bed depth, but goes with the fourth power of the gradient of the bed and with the fifth power of the width of the stream. We show that the theoretically derived scaling relation is supported by the observed velocity scaling of outlet glaciers across Greenland as well as by idealized numerical simulations of marine ice-sheet instabilities (MISIs) as found in Antarctica. Assuming a proportionality between the flow itself and its spatial derivative, we combine the scaling relation with a statistical analysis of the topography of 13 MISI-prone Antarctic outlets. Under these assumptions the timescales in response to a potential destabilization are fastest for Thwaites Glacier in West Antarctica and Mellor, Ninnis and Cook Glaciers in East Antarctica; between 16 and 67 times faster than for Pine Island Glacier. While the applicability of our results is limited by several strong assumptions, the utilization and potential further development of the presented scaling approach may help to constrain time-scale estimates of outlet glacier-flow, augmenting the commonly exploited and comparatively computationally expensive approach of numerical modeling.

show abstract

Scaling of instability timescales of Antarctic outlet glaciers based on one-dimensional similitude analysis

Cited by 8 publications

References 67 publications

The stability of present-day Antarctic grounding lines – Part A: No indication of marine ice sheet instability in the current geometry

The stability of present-day Antarctic grounding lines – Part A: No indication of marine ice sheet instability in the current geometry

On the History and Future of 100% Renewable Energy Systems Research

Timescales of outlet-glacier flow with negligible basal friction: Theory, observations and modeling

Contact Info

Product

Resources

About