A periodic visco-elastic model for crevasses propagation in marine ice shelves
Bibliographic record
Abstract
Calving is a key mechanism that controls the length of floating ice shelves, and therefore theirbuttressing effect on grounded ice. A fully process-based model for calving is currently still notavailable in a form suitable for large-scale ice sheet models. Here we build on prior work thattreats crevasse growth in the run-up to calving as an example of linear elastic fracture growth.Purely elastic behaviour is confined to short time intervals, much less than a single Maxwelltime (the ratio of viscosity to Young’s modulus) in duration: this is typically hours to a few daysfor cold polar ice shelves, depending on temperature and state of stress. We explicitly recognizethat the elastic stresses occurring during fracture propagation act on an ice-mass subject to apre-stress created by long-term viscous deformation. By coupling a boundary element solverfor instantaneous elastic stress increments and the resulting fracture propagation with theElmer/Ice Stokes flow solver that computes the pre-stress and is able to model the long-termevolution of the domain, we are able to show how viscous deformation end elastic fracturemechanics interact. We show that viscous deformation is in general an essential part of calving,and as a result, viscous deformation ultimately sets the time scale for calving. The geometricchanges resulting from that deformation are necessary to cause continued growth to calvingof fractures that initially propagate only part-way through the domain. We identify two distinctmodes of fracture propagation: either fractures propagate episodically, the crack lengthening ineach instance by a finite difference over short (elastic) time scales. Alternatively, fractures growgradually in such a way as to keep the viscous pre-stress near the crack tip from becomingtensile, with elasticity playing a secondary role. Our results point to the purely instantaneousstress-based calving laws that have become popular in large-scale ice sheet mechanics beingtoo simplistic. Figure1: ice shelf geometry evolution and crevasse propagation
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.003 | 0.001 |
| Insufficient payload (model declined to judge) | 0.005 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".