ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

3aUW2. Seismoacoustic observations as related to thermally induced stresses and fracturing in pack ice.

James K. Lewis

Ocean Phys. Res. & Dev., 207 S. Seashore Ave., Long Beach, MS 39560

On-ice geophone data and under-ice noise data contain a significant amount of information about the stress state of pack ice and how ice fractures in response to the stress. This information can be used to study the rheology of sea ice and the related mechanics of fracturing. A review is presented of the current understanding of ice mechanics related to thermal fracturing based on seismoacoustic observations. A rheology is presented and discussed based on a thermodynamic model and an associated stress/strain relationship. The rheology has an enhancement which prescribes how the extent of existing cracks in the ice affect (1) the stress state of the ice, (2) the number of fractures when the ice exceeds its yield strength, and (3) the stress relief after fracturing occurs. This allows us to simulate first-year and multiyear ice using the same model by differentiating the two ice types based on the extent of existing cracks. Examples are shown of how under-ice acoustic data can be used to estimate the vertical distribution of the fractional area of existing cracks in multiyear ice.