Linking Sea Ice Deformation to Ice Thickness Redistribution Using High-Resolution Satellite Radar and Airborne Ice Thickness Observations
Dynamic processes can contribute more than 50% to the total thickness of deformed sea ice. They gain importance in the context of a changing Arctic, in which reduced ice thickness and increased drift speed enhance deformation events that might compensate the thermodynamic thinning. The case study of...
| Main Authors: | , , |
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| Format: | Conference Object |
| Language: | unknown |
| Published: |
2020
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| Subjects: | |
| Online Access: | https://epic.awi.de/id/eprint/53406/ https://epic.awi.de/id/eprint/53406/1/AGU_vonAlbedyll.zip https://hdl.handle.net/10013/epic.37977a26-104b-47b5-89e7-21c093f9299e https://hdl.handle.net/ |
| Summary: | Dynamic processes can contribute more than 50% to the total thickness of deformed sea ice. They gain importance in the context of a changing Arctic, in which reduced ice thickness and increased drift speed enhance deformation events that might compensate the thermodynamic thinning. The case study of an unusual, large polynya that opened and then closed by freezing and convergence north of the coast of Greenland in late winter 2018 offers us the unique chance to study the effects of dynamics on ice thickness in detail. We calculated drift and deformation fields for the closing phase of the polynya from a time series of daily Synthetic Aperture Radar (SAR) satellite images and measured the accumulated effects of dynamic and thermodynamic ice growth with an airborne electromagnetic (AEM) ice thickness survey one month after the closing began. We observed that strong ice convergence decreased the area of the former polynya by a factor of 2.5 while the AEM survey indicated mean and modal thicknesses of the one-month old ice of 1.96 and 0.95 m, respectively. This is in close agreement with the calculated thermodynamic growth and with the dynamic thickening expected from the polynya area decrease. Further, we identified characteristic differences in the shapes of ice thickness distributions in different regions of the closing polynya that are linked to the deformation histories of the ice. We reconstructed the deformation history by combining Lagrangian backward trajectories with the deformation fields derived from high-resolution SAR imagery. We found a linear proportionality between convergence and thickness change in good agreement with ice thickness redistribution theory. Further, we identified a proportionality between the e-folding of the tails of the different ice thickness distributions and the magnitude of the total deformation experienced by the ice. Lastly, we developed a simple volume-conserving model to derive dynamic ice thicknesses change from high-resolution SAR deformation tracking. Model and AEM observations agree reasonably well and the derived ice thickness distribution reproduce main characteristics like mode, width, and e-folding of the observed distribution. Hence, this shows that high-resolution SAR deformation observations are capable of producing realistic ice thickness distributions. |
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