Extracting iceberg freeboard using shadow length in high-resolution optical images
Icebergs are big chunks of ice floating on the ocean surface, and melting of icebergs contributes for the major part of freshwater flux into ocean. Dynamic monitoring of the icebergs in Antarctica and accurate estimation of their volume are important for predicting the trend of freshwater budget of...
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ftdoajarticles:oai:doaj.org/article:0e0c4ca4493e4e1a87fc7c47c0edad2c 2024-09-15T17:48:14+00:00 Extracting iceberg freeboard using shadow length in high-resolution optical images Ziyi Suo Yingcheng Lu Jianqiang Liu Jing Ding Qing Wang Ling Li Weimin Ju Manchun Li 2024-05-01T00:00:00Z https://doi.org/10.1080/10095020.2024.2360525 https://doaj.org/article/0e0c4ca4493e4e1a87fc7c47c0edad2c EN eng Taylor & Francis Group https://www.tandfonline.com/doi/10.1080/10095020.2024.2360525 https://doaj.org/toc/1009-5020 https://doaj.org/toc/1993-5153 doi:10.1080/10095020.2024.2360525 1993-5153 1009-5020 https://doaj.org/article/0e0c4ca4493e4e1a87fc7c47c0edad2c Geo-spatial Information Science, Vol 27, Iss 3, Pp 892-901 (2024) Optical remote sensing iceberg freeboard shadow length HY-1C/D CZI Sentinel-2 MSI Mathematical geography. Cartography GA1-1776 Geodesy QB275-343 article 2024 ftdoajarticles https://doi.org/10.1080/10095020.2024.2360525 2024-08-05T17:48:57Z Icebergs are big chunks of ice floating on the ocean surface, and melting of icebergs contributes for the major part of freshwater flux into ocean. Dynamic monitoring of the icebergs in Antarctica and accurate estimation of their volume are important for predicting the trend of freshwater budget of the Southern Ocean. The iceberg freeboard is a key parameter for measuring the thickness and volume of an iceberg and is defined as the difference between the elevation of iceberg surface and sea level. So far, freeboards of icebergs have been successfully extracted using InSAR DEM, and the laser and radar altimeter. However, uncertainties exist in these results mainly caused by missed detection of small icebergs due to the spatially sparse and temporally incomplete data coverage. In addition to the above techniques, optical images can also be used to extract the iceberg freeboard based on its geometric relationship with shadow length, which can effectively compensate for the above shortcomings. Although the feasibility has been preliminarily presented, the precision and extensive application of shadow-height method deserves further research, such as estimating the basal melting of icebergs. In this work, we tested an optical image-based freeboard extraction method over icebergs in Prydz Bay, Antarctica. A normalized shadow pixel index (NSPI) is designed to identify iceberg shadows with different shapes in HY-1C/D CZI and Sentinel-2 MSI optical images. The iceberg freeboard can be determined with an acceptable precision (2 m) in optical images compared with laser altimeter (i.e. ICESat-2) measurements. Moreover, basal melting of icebergs has been assessed according to the variation of freeboard using repeated optical observations. The results indicate that icebergs in the study area were with a mean freeboard of about 56 m in early December 2022, and experienced a decrease in freeboard of 1.9 m within two months, in correspondence with the Antarctic seasonal trend. The methodological framework, therefore, turns out to ... Article in Journal/Newspaper Antarc* Antarctic Antarctica Iceberg* Prydz Bay Southern Ocean Directory of Open Access Journals: DOAJ Articles Geo-spatial Information Science 27 3 892 901 |
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Open Polar |
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Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Optical remote sensing iceberg freeboard shadow length HY-1C/D CZI Sentinel-2 MSI Mathematical geography. Cartography GA1-1776 Geodesy QB275-343 |
spellingShingle |
Optical remote sensing iceberg freeboard shadow length HY-1C/D CZI Sentinel-2 MSI Mathematical geography. Cartography GA1-1776 Geodesy QB275-343 Ziyi Suo Yingcheng Lu Jianqiang Liu Jing Ding Qing Wang Ling Li Weimin Ju Manchun Li Extracting iceberg freeboard using shadow length in high-resolution optical images |
topic_facet |
Optical remote sensing iceberg freeboard shadow length HY-1C/D CZI Sentinel-2 MSI Mathematical geography. Cartography GA1-1776 Geodesy QB275-343 |
description |
Icebergs are big chunks of ice floating on the ocean surface, and melting of icebergs contributes for the major part of freshwater flux into ocean. Dynamic monitoring of the icebergs in Antarctica and accurate estimation of their volume are important for predicting the trend of freshwater budget of the Southern Ocean. The iceberg freeboard is a key parameter for measuring the thickness and volume of an iceberg and is defined as the difference between the elevation of iceberg surface and sea level. So far, freeboards of icebergs have been successfully extracted using InSAR DEM, and the laser and radar altimeter. However, uncertainties exist in these results mainly caused by missed detection of small icebergs due to the spatially sparse and temporally incomplete data coverage. In addition to the above techniques, optical images can also be used to extract the iceberg freeboard based on its geometric relationship with shadow length, which can effectively compensate for the above shortcomings. Although the feasibility has been preliminarily presented, the precision and extensive application of shadow-height method deserves further research, such as estimating the basal melting of icebergs. In this work, we tested an optical image-based freeboard extraction method over icebergs in Prydz Bay, Antarctica. A normalized shadow pixel index (NSPI) is designed to identify iceberg shadows with different shapes in HY-1C/D CZI and Sentinel-2 MSI optical images. The iceberg freeboard can be determined with an acceptable precision (2 m) in optical images compared with laser altimeter (i.e. ICESat-2) measurements. Moreover, basal melting of icebergs has been assessed according to the variation of freeboard using repeated optical observations. The results indicate that icebergs in the study area were with a mean freeboard of about 56 m in early December 2022, and experienced a decrease in freeboard of 1.9 m within two months, in correspondence with the Antarctic seasonal trend. The methodological framework, therefore, turns out to ... |
format |
Article in Journal/Newspaper |
author |
Ziyi Suo Yingcheng Lu Jianqiang Liu Jing Ding Qing Wang Ling Li Weimin Ju Manchun Li |
author_facet |
Ziyi Suo Yingcheng Lu Jianqiang Liu Jing Ding Qing Wang Ling Li Weimin Ju Manchun Li |
author_sort |
Ziyi Suo |
title |
Extracting iceberg freeboard using shadow length in high-resolution optical images |
title_short |
Extracting iceberg freeboard using shadow length in high-resolution optical images |
title_full |
Extracting iceberg freeboard using shadow length in high-resolution optical images |
title_fullStr |
Extracting iceberg freeboard using shadow length in high-resolution optical images |
title_full_unstemmed |
Extracting iceberg freeboard using shadow length in high-resolution optical images |
title_sort |
extracting iceberg freeboard using shadow length in high-resolution optical images |
publisher |
Taylor & Francis Group |
publishDate |
2024 |
url |
https://doi.org/10.1080/10095020.2024.2360525 https://doaj.org/article/0e0c4ca4493e4e1a87fc7c47c0edad2c |
genre |
Antarc* Antarctic Antarctica Iceberg* Prydz Bay Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctica Iceberg* Prydz Bay Southern Ocean |
op_source |
Geo-spatial Information Science, Vol 27, Iss 3, Pp 892-901 (2024) |
op_relation |
https://www.tandfonline.com/doi/10.1080/10095020.2024.2360525 https://doaj.org/toc/1009-5020 https://doaj.org/toc/1993-5153 doi:10.1080/10095020.2024.2360525 1993-5153 1009-5020 https://doaj.org/article/0e0c4ca4493e4e1a87fc7c47c0edad2c |
op_doi |
https://doi.org/10.1080/10095020.2024.2360525 |
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Geo-spatial Information Science |
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901 |
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