Abstract
Landfast ice is an integral component of the coastal ecosystem. Extracting the edge and mapping the extent of landfast ice are one of the main methods for studying ice changes. In this work, a standardized process for extracting landfast ice edge in the Baltic Sea using the InSAR coherence image is established with Sentinel-1 radar data and InSAR technology. A modified approach combining multiscale segmentation and morphological erosion is then proposed to provide a reliable way to extract landfast ice edge. Firstly, the coherence image is obtained using InSAR technology. Then, the edge is separated and extracted with the modified approach. The modified approach is essentially a four-step procedure involving image segmentation, median filter, morphological erosion, and rejection of small patches. Finally, the full extent of landfast ice can be obtained using floodfill algorithm. Multiple InSAR image pairs of Sentinel-1A acquired from 2018 to 2019 are utilized to successfully extract the landfast ice edge in the Gulf of Bothnia. The results show that the landfast ice edge and the extents obtained by the proposed approach are visually consistent with those shown in the ice chart issued by the Swedish Meteorological and Hydrological Institute (SMHI) over a coastline length of 345 km. The mean distance between land–water boundary and the coastline issued by the National Oceanic and Atmospheric Administration (NOAA) is 109.1 m. The modified approach obviously preserves more details in local edge than the reference method. The experimental results show that the modified approach proposed in this paper can extract the edge and map the extent of landfast ice more accurately and quickly, and is therefore expected to contribute to the further understanding and analyzing the changes of landfast ice in the future.
Highlights
IntroductionSea ice is sensitive to climate change and is known as an indicator of global climate change
As this study focuses on the clear edge of landfast ice, holes in the main body are of less importance
With the interferometric coherence image, a modified approach of extracting the landfast ice edge based on mul
Summary
Sea ice is sensitive to climate change and is known as an indicator of global climate change. It plays a vital role in marine hydrology, atmospheric circulation, and material exchange. It directly affects human social activities such as fishery and ocean transportation. Annual formation time and extent of landfast ice changes to varying degrees. These changes are important for effective monitoring of sea ice extent, responding to sea ice disasters, and guiding the construction of ice roads in near-polar coastal areas (such as the Baltic Sea and Greenland). With the development of remote sensing technology, regularly obtaining large-scale information from space has become an effective method for sea ice identification and monitoring [7,8]
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