Abstract
ABSTRACTThe permeability of sea ice can strongly affect the dissipation of wave energy into the ice pack. Sea-ice permeability is known to be impacted by the brine volume fraction and the blockage of flow pathways by the freezing of infiltrating lower salinity water. Here we investigate another process impacting sea-ice permeability, namely, inelastic deformation. We report the results of a first-of-its-kind field-scale deformation experiment to investigate the impact of compressive loading on sea-ice permeability. We observed that deformation decreased permeability by four orders of magnitude or more in some locations, while elsewhere permeability was unaffected or possibly increased. We show that the observed changes in permeability are consistent with expected changes in stress state and, as a result, in the mechanisms of deformation.
Highlights
As sea-ice extent in polar regions decreases (e.g., Stroeve and others, 2012), increasing open water fetches are generating larger waves (Thomson and others, 2016), which may propagate farther into the pack ice and potentially break it up (Asplin and others, 2012; Thomson and Rogers, 2014)
Marchenko and Cole (2017) found that when the saline ice permeability is >10−9 cm2, corresponding to a brine volume fraction of ∼5% (Golden and others, 2007), wave-energy dissipation is dominated by the migration of liquid brine through the ice, highlighting the important role of ice permeability on wave-energy dissipation
As the applied compressive stress of ∼0.75 MPa is less than the compressive strength of the ice, it is likely that any grain refinement ahead of the indentor was limited/negligible and this process is likely not a significant contributor to permeability changes in our experiments
Summary
As sea-ice extent in polar regions decreases (e.g., Stroeve and others, 2012), increasing open water fetches are generating larger waves (Thomson and others, 2016), which may propagate farther into the pack ice and potentially break it up (Asplin and others, 2012; Thomson and Rogers, 2014). Failure likely occurs due to wave-induced bending of the ice cover, which induces cyclic compressional and tensional stresses in the ice. The stress amplitude of loading is proportional to the wave amplitude and depends on the wave attenuation along the ray of wave propagation below the ice. Potentially destructive compressional stresses due to wave-induced bending are enhanced when wind pushes the ice perpendicular to a coastline (Tremblay and Hakakian, 2006). Destructive compressional stresses due to wave-induced bending are enhanced when wind pushes the ice perpendicular to a coastline (Tremblay and Hakakian, 2006) These processes are more likely to operate in the late summer and early fall when the ice is warm and the fetch long. Field observations of wave events in the Barents Sea have shown that wave damping is stronger in solid ice and reduced significantly when the ice is broken into floes by waves (Collins and others, 2015). Marchenko and Cole (2017) found that when the saline ice permeability is >10−9 cm, corresponding to a brine volume fraction of ∼5% (Golden and others, 2007), wave-energy dissipation is dominated by the migration of liquid brine through the ice, highlighting the important role of ice permeability on wave-energy dissipation
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