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MS Thesis Defense: Michael May

Jul

12

Tuesday
10:00am - 11:00am ET

Jackson Conf Rm, Cummings Hall

"The impact of contact geometry on sea ice stress and fracture at the scale of ice floes"

Abstract

Observations of stress and strain at the scale of ice floes are necessary to fill a gap in our understanding of sea ice mechanical behavior. Current climate and ice dynamics models represent ice mechanical properties using stress-strain relationships largely determined at laboratory-scale (<1m) or from regional-scale (10+km) deformation observations. The former scale does not include all mechanisms of deformation operating in the ice pack; the latter aggregates multiple modes of deformation into non-physical fluid analogies. The Sea Ice Dynamics Experiment (SIDEx) was run in Feb-Mar 2021 to fill this gap, observing stress and strain at the scale of sea ice failure processes. Here we present stress sensor observations. Stress gages (N=31) were deployed over a 4.5km2 area in the southern Beaufort Sea to observe in-situ stress.

These data were analyzed in the context of deformation observations from satellite imagery and local laser and radar interferometers to explain the drivers of sea ice stress variations before and after fracture. Three case studies between 14 March and 24 March, during which fractures propagated through the stress observing array, are presented here. We find that the contact geometry between floes, along with the regional motion that is driving the floes to interact, is consistent with the observed stress state, fracture, and orientation of stress post-fracture at local scale. When the floe is contiguous and fractures are far away, stress magnitude and orientation is similar across the entire domain and changes are highly correlated. As the floe fractures, spatial variability in stress increases and high stresses are found along the floe contacts. Peak stresses occur on or near contacting asperities, reaching up to 600 kPa, and along paths connecting contact points. The interrelation between stress state and geometry suggests that high fidelity models, initialized with realistic floe geometry, may have deterministic predictive capability for further ice fracture.

Thesis Committee

  • Christopher Polashenski, PhD
  • Donald Perovich, PhD
  • Erland Schulson, PhD

Contact

For more information, contact Theresa Fuller at theresa.d.fuller@dartmouth.edu.