Exploring Small-Scale Movement and Deformation of Landfast Sea Ice through InSAR Observations and Pseudo-Inverse Modeling

Abstract:

Arctic landfast sea ice provides important services to local populations, industry and key marine biota. Such services strongly depend on the stability of the landfast ice cover. While landfast ice may appear stationary to the untrained eye, it is in fact constantly undergoing changes, many of them a result of deformation and movement on scales of meters or less. Such processes, while difficult to detect, are closely linked to important coastal hazards, including the formation of cracks (with potential for flooding or hazardous drainage during the melt season) and catastrophic breakout and complete removal of landfast ice. This study applies synthetic aperture radar interferometry (InSAR) in combination with modeling to characterize direction and magnitude of deformation through maximizing coherence between forward models. The model has been tested using ALOS-1 L-band (2010) and ERS-2 C-band (1992) SAR collected over coastal sea ice in northern Alaska. It correctly identifies convergence in the ice cover of coastal lagoons where thermal contraction and tidal forcing are known to be primary causes of ice deformation. Sea ice interferograms are complex and avoiding phase unwrapping leads to more unstable solutions. Therefore areas exposed to higher wind stress and interaction with the offshore pack ice, model results are less definitive and require analysis in terms of plausible forcing mechanisms. Interpretation of InSAR data over landfast sea ice has provided insights into the extent of bottomfast ice. The data also hold promise in evaluating the impact of artificial gravel islands on ice stability and tracking potentially hazardous displacement along ice roads used by industry.