Sea ice monitoring in the Arctic using satellite SAR images

• Main Author: WÃ¥hlin, Johan
• Format: Bachelor Thesis
• Language: English
• Published: 2007
• Subjects: Technology; Teknik; Arctic; Barents Sea; Sea ice
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-54045

Synthetic Aperture Radar (SAR) with its high resolution and capability to see through clouds is suitable for studying sea ice, an important parameter for global climate but which due to its remoteness little is known about. To study the motion of sea ice, manual drift vectors have been acquired from every three days from Envisat SAR wide swath image pairs with 150 m resolution. These vectors have been compared with other ice drift products of lower resolution, a sea ice model and data from drifting buoys in the north east Barents Sea. The SAR wide swath drift vectors agreed well with the buoy data on the one occasion a comparison was possible. They also proved to give more details and to be more exact close to land than lower resolution radar products. The validation of the model was useful, it was good in predicting the direction of the ice drift, however it proved much too slow. Following a ship drifting across the Arctic the manual ice drift vectors were used to study ice drift leading to deformation of the pack ice, so called differential ice drift. By colour coding drift vectors after length and plotting them on a SAR image, differential drift became apparent. It proved that the spatial resolution of the SAR images was enough to detect divergence and shear features only a few kilometres wide. Convergent motion could also be seen, but the subsequent ridging was difficult to spot due to the small size of ridges. The study also showed how quickly sea ice drift can change direction and speed, so to get a more complete picture of drift and deformation, SAR images should be acquired as often as possible. During field work, measurements on sea ice were made, i.e. ice freeboard and thickness, snow thickness and density and ice density and salinity. These measurements showed that a method that is planned to be used from satellites to deduct the sea ice thickness was very sensitive to changes in snow depth and density. These are properties that can not be measured from satellites. Validerat; 20101217 (root)