Abstract
Mapping of fast ice displacement and investigating sea ice rheological behavior is a major open topic in coastal ice engineering and sea ice modeling. This study presents first results on Sentinel-1 repeat-pass space borne synthetic aperture radar interferometry (InSAR) in the Gulf of Bothnia over the fast ice areas. An InSAR pair acquired in February 2015 with a temporal baseline of 12 days has been studied here in detail. According to our results, the surface of landfast ice in the study area was stable enough to preserve coherence over the 12-day baseline, while previous InSAR studies over the fast ice used much shorter temporal baselines. The advantage of longer temporal baseline is in separating the fast ice from drift ice and detecting long term trends in deformation maps. The interferogram showed displacement of fast ice on the order of 40 cm in the study area. Parts of the displacements were attributed to forces caused by sea level tilt, currents, and thermal expansion, but the main factor of the displacement seemed to be due to compression of the drift ice driven by southwest winds with high speed. Further interferometric phase and the coherence measurements over the fast ice are needed in the future for understanding sea ice mechanism and establishing sustainability of the presented InSAR approach for monitoring dynamics of the landfast ice with Sentinel-1 data.
Highlights
Landfast sea ice is a type of sea ice that is formed and fastened to the coastline, islands, grounded ridges or any fixed objects in waters
We examine the potential of Sentinel-1 data, even with a temporal baseline of 12 days, to detect, monitor and quantify the landfast ice displacement under certain conditions
An area nearly 400 km2 was found with well-defined fringes and total change in the line of sight (LOS) of 40 cm
Summary
Landfast sea ice is a type of sea ice that is formed and fastened to the coastline, islands, grounded ridges or any fixed objects in waters. The drift ice moving by winds and sea currents is found and forms an interactive outer boundary for the landfast ice. In the Baltic Sea, this boundary can reach the isobaths of 5–15 m depending on how cold the winter is [1]. In extreme forcing conditions, the landfast ice may break and move horizontally, scouring of the sea bottom, and loading of the coastline and man-made structures take place [1]. These events put coastal structures, beacons and on-ice traffic in danger, and compromise safety for working on the ice. After the start of the melting season in the spring, ice floes and ridges may drift causing increased land-ice interaction and coastal erosion.
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