the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 12 Sep 2023
Arctic shoreline displacement with open satellite imagery and data fusion: A pilot study 1984–2022
Abstract. The Arctic coast is facing rapid changes due to thawing permafrost and melting glaciers and sea ice. Communities all around the Arctic urgently need local-scale information on coastal change. This study aimed at developing a scalable and transferable procedure for mapping shoreline displacement in Arctic conditions by using an archive of satellite images. Our approach utilizes cloud computing in Google Earth Engine to process a large number of open satellite images for large areas and a long period of time (here 39 years). The procedure was iteratively developed in two contrasting study areas in Arctic Norway. It applies data fusion (including sensor fusion, algorithm fusion, and decision fusion) to improve classification accuracy and processing efficiency. For one 2 500 km2 area of interest, the procedure utilizes c. 600 satellite images to create coastal land cover and shoreline time series in less than one hour. Data fusion reduces problems related to the low availability and quality of satellite data in the Arctic before 2013 and reduces the impacts of noise and short-term changes. However, low data availability tends to create local gaps in the time series. Validation in the Tanafjorden and north-western Svalbard coasts indicates an overall classification accuracy of more than 99 % (against an independent sample of 2000 coastal points) and a median shoreline error distance of less than 15 m (against manually digitized shoreline) in 2019–2022. We exemplify how the method produces new information for identifying coastal change hotspots and examining long-term trends and local scale processes. We give examples of glacier retreat, spit migration, and delta development. This procedure is scalable and transferable to any coastal area demonstrating potential for producing the first circumpolar dataset of shoreline displacement.
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Status: closed
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RC1: 'Comment on egusphere-2023-1399', Ionut Cristi Nicu, 25 Sep 2023
Dear Authors,
In order to be published in The Cryosphere journal, your manuscript needs substantial reviews. The Introduction section needs to be improved by highlighting the most recent advances in the field and updating your reference list. For a paper like this, the reference list is very short. This may show a poor understanding of the Arctic area and what has been done until now. Also, it is highly indicated that you improve the manuscript's clarity. Maybe you should move the Study area section before the Methods. To have more credibility, I would also add one more validation area, e.g. the coast of Canada that is highlighted in the study of Irrgang. I think that two study areas are just not enough to prove that your method is feasible. More detailed comments are highlighted in the attached .pdf file.
Kind regards.
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AC1: 'Reply on RC1', Tua Nylén, 23 Oct 2023
Dear Referee,
We thank you for the comments and suggestions! Please find below our response to the three main comments, and description of changes made for the revised manuscript. Below the three points, we also respond to two comments found in the pdf. Other comments found in the pdf have been carefully taken into account and suggested edits have been made when revising the manuscript.
1.
Comment from referee: "The Introduction section needs to be improved by highlighting the most recent advances in the field and updating your reference list. For a paper like this, the reference list is very short. This may show a poor understanding of the Arctic area and what has been done until now."
Author’s response: We have added c. 15 new references that represent the most recent knowledge of the Arctic coastal environment and recent studies on coastal change.
2.
Comment from referee: "Also, it is highly indicated that you improve the manuscript's clarity. Maybe you should move the Study area section before the Methods."
Author’s response: We have made this change to the structure of the manuscript. Namely, we have now a new level 1 heading “2. Study areas” and the numbering of figures and subsequent headings has been edited (“3. Methods” etc.). We have also added a new level 2 heading: “3.1 Proposed procedure for Arctic shoreline displacement time-series” to structure the method description. Please see also below our response to the comment regarding the length and level of detail of the Methods section.
3.
Comment from referee: "To have more credibility, I would also add one more validation area, e.g. the coast of Canada that is highlighted in the study of Irrgang. I think that two study areas are just not enough to prove that your method is feasible."
Author’s response: Testing the applicability of the proposed method all around the Arctic is beyond the scope of this pilot study. This study aimed at testing the capabilities of the procedure, not yet it’s applicability in the whole Arctic. Eventually, the outputs of the (final) procedure will be fully validated in diverse environments around the Arctic in a subsequent publication. Based on the comment, we have clarified the scope of the study in the abstract, Introduction and Discussion. In the abstract, for example, we will say: “This study aimed at developing and demonstrating the capabilities of a scalable and transferable procedure for mapping shoreline displacement in the Arctic conditions, by using an archive of satellite images.” and at the end “Based on the examined capabilities of the proposed procedure, it is scalable and transferable to other coastal areas, and therefore demonstrates potential for producing the first circumpolar dataset of shoreline displacement.”
4. (comment in the pdf)
Comment from referee (page 3 of the pdf): "This section needs to be more elaborated."
Author’s response: This general comment was assigned to the Methods section. There were also other comments asking why details are given in the Supplement instead of the manuscript. This is because of the tight paper format of the journal. As far as we understand, the manuscript cannot be extended, at least without leaving out existing content. We have carefully used all space, leaving out those technical and methodological details that are not absolutely necessary for understanding the main steps of the procedure, or the validation. The Supplement serves as a full methodological description. We will need to wait for instructions of the handling editor, before making decisions about expanding the manuscript.
5. (comment in the pdf)
Comment from referee (page 6 of the pdf): "Specify at least the spatial resolution."
Author’s response: This comment was assigned to the following sentence: “For this paper, we manually checked the possibility of including the lower-quality tier 2 Landsat 5 and Landsat 7 images to increase the number of observations but found that their quality was not sufficient.” In this context, the spatial resolution is not relevant. The poor quality of the tier 2 images mainly refers to the larger geometrical errors, leading to horizontal displacement. We specified this in the text: “For this paper, we manually checked the possibility to include the lower-quality tier 2 Landsat 5 and Landsat 7 images to increase the number of observations but found that their quality was not sufficient. Namely, their large geometrical errors (> 12 m radial root mean square error) led to horizontal inaccuracies that had negative impacts on the land cover classification accuracy.”
The manuscript has now been revised and we are waiting for further instructions from the editorial board of The Cryosphere.
Best regards
Tua Nylén, on behalf of all authors
Citation: https://doi.org/10.5194/egusphere-2023-1399-AC1
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AC1: 'Reply on RC1', Tua Nylén, 23 Oct 2023
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RC2: 'Comment on egusphere-2023-1399', Anonymous Referee #2, 13 Feb 2024
Dear Authors,
The manuscript presents an interesting methodological approach that certainly deserves attention for the digitization of the sea shoreline position, based on series of satellite imagery. The developed tool was tested by the authors on two sites of the coast of Norway, which certainly belong to the Arctic, but are quite specific. These areas are characterized by the distribution of predominantly rocky and coarse built coastal bluffs, and with the same success this procedure can be applied to the coasts of any climate zones of Earth.
In essence, a universal tool is proposed, which, like DSAS, is not limited by the Arctic, and therefore the choice of The Cryosphere as a journal for publication does not seem obvious. Moreover, the results obtained are not interpreted by the authors in any way from the point of view of the peculiarities of the evolution of the Arctic coasts; the role of the geomorphological structure of the coasts, the presence of permafrost and its ice content is not considered in any way, which is the subject of discussion in publications on the landscape dynamics within Earth’s cryosphere. The information given in the Introduction about the dynamics of the Arctic coasts, built by the ice-rich permafrost does not correspond to the characteristics of the study areas. Actually, the manuscript does not contain a detailed description of the study areas, such as the structural features of the coastal cliffs, the onshore and offshore geomorphology, the sediments composition along the coastline, permafrost characteristics and ground ice presence.
The Discussion section discusses mainly technical details, such as classification accuracy and the position of the obtained coastlines from the reference ones. There is no geomorphological interpretation of the results obtained in the manuscript, nor is it in section 3.3 Examples of geomorphological applications. The natural component that makes the Arctic coasts a special, in many ways unique object of study is not highlighted in the article.
Thus, the authors have proposed an interesting approach for studying coastal dynamics with a comprehensive analysis of a time series of satellite imagery, but the manuscript is still just methodological. In light of the above, it seems to me that the proposed manuscript is not entirely suitable for The Cryosphere journal, but is more consistent with the topics of EGU journals focused on geoscientific, geoinformation methods and approach. Therefore, I suggest that authors consider the possibility of redirecting the manuscript to one of the following EGU journals: 1) Geoscientific Instrumentation, Methods and Data Systems (GI) or 2) Geoscientific Model Development (GMD).
kind regards
Citation: https://doi.org/10.5194/egusphere-2023-1399-RC2
Status: closed
-
RC1: 'Comment on egusphere-2023-1399', Ionut Cristi Nicu, 25 Sep 2023
Dear Authors,
In order to be published in The Cryosphere journal, your manuscript needs substantial reviews. The Introduction section needs to be improved by highlighting the most recent advances in the field and updating your reference list. For a paper like this, the reference list is very short. This may show a poor understanding of the Arctic area and what has been done until now. Also, it is highly indicated that you improve the manuscript's clarity. Maybe you should move the Study area section before the Methods. To have more credibility, I would also add one more validation area, e.g. the coast of Canada that is highlighted in the study of Irrgang. I think that two study areas are just not enough to prove that your method is feasible. More detailed comments are highlighted in the attached .pdf file.
Kind regards.
-
AC1: 'Reply on RC1', Tua Nylén, 23 Oct 2023
Dear Referee,
We thank you for the comments and suggestions! Please find below our response to the three main comments, and description of changes made for the revised manuscript. Below the three points, we also respond to two comments found in the pdf. Other comments found in the pdf have been carefully taken into account and suggested edits have been made when revising the manuscript.
1.
Comment from referee: "The Introduction section needs to be improved by highlighting the most recent advances in the field and updating your reference list. For a paper like this, the reference list is very short. This may show a poor understanding of the Arctic area and what has been done until now."
Author’s response: We have added c. 15 new references that represent the most recent knowledge of the Arctic coastal environment and recent studies on coastal change.
2.
Comment from referee: "Also, it is highly indicated that you improve the manuscript's clarity. Maybe you should move the Study area section before the Methods."
Author’s response: We have made this change to the structure of the manuscript. Namely, we have now a new level 1 heading “2. Study areas” and the numbering of figures and subsequent headings has been edited (“3. Methods” etc.). We have also added a new level 2 heading: “3.1 Proposed procedure for Arctic shoreline displacement time-series” to structure the method description. Please see also below our response to the comment regarding the length and level of detail of the Methods section.
3.
Comment from referee: "To have more credibility, I would also add one more validation area, e.g. the coast of Canada that is highlighted in the study of Irrgang. I think that two study areas are just not enough to prove that your method is feasible."
Author’s response: Testing the applicability of the proposed method all around the Arctic is beyond the scope of this pilot study. This study aimed at testing the capabilities of the procedure, not yet it’s applicability in the whole Arctic. Eventually, the outputs of the (final) procedure will be fully validated in diverse environments around the Arctic in a subsequent publication. Based on the comment, we have clarified the scope of the study in the abstract, Introduction and Discussion. In the abstract, for example, we will say: “This study aimed at developing and demonstrating the capabilities of a scalable and transferable procedure for mapping shoreline displacement in the Arctic conditions, by using an archive of satellite images.” and at the end “Based on the examined capabilities of the proposed procedure, it is scalable and transferable to other coastal areas, and therefore demonstrates potential for producing the first circumpolar dataset of shoreline displacement.”
4. (comment in the pdf)
Comment from referee (page 3 of the pdf): "This section needs to be more elaborated."
Author’s response: This general comment was assigned to the Methods section. There were also other comments asking why details are given in the Supplement instead of the manuscript. This is because of the tight paper format of the journal. As far as we understand, the manuscript cannot be extended, at least without leaving out existing content. We have carefully used all space, leaving out those technical and methodological details that are not absolutely necessary for understanding the main steps of the procedure, or the validation. The Supplement serves as a full methodological description. We will need to wait for instructions of the handling editor, before making decisions about expanding the manuscript.
5. (comment in the pdf)
Comment from referee (page 6 of the pdf): "Specify at least the spatial resolution."
Author’s response: This comment was assigned to the following sentence: “For this paper, we manually checked the possibility of including the lower-quality tier 2 Landsat 5 and Landsat 7 images to increase the number of observations but found that their quality was not sufficient.” In this context, the spatial resolution is not relevant. The poor quality of the tier 2 images mainly refers to the larger geometrical errors, leading to horizontal displacement. We specified this in the text: “For this paper, we manually checked the possibility to include the lower-quality tier 2 Landsat 5 and Landsat 7 images to increase the number of observations but found that their quality was not sufficient. Namely, their large geometrical errors (> 12 m radial root mean square error) led to horizontal inaccuracies that had negative impacts on the land cover classification accuracy.”
The manuscript has now been revised and we are waiting for further instructions from the editorial board of The Cryosphere.
Best regards
Tua Nylén, on behalf of all authors
Citation: https://doi.org/10.5194/egusphere-2023-1399-AC1
-
AC1: 'Reply on RC1', Tua Nylén, 23 Oct 2023
-
RC2: 'Comment on egusphere-2023-1399', Anonymous Referee #2, 13 Feb 2024
Dear Authors,
The manuscript presents an interesting methodological approach that certainly deserves attention for the digitization of the sea shoreline position, based on series of satellite imagery. The developed tool was tested by the authors on two sites of the coast of Norway, which certainly belong to the Arctic, but are quite specific. These areas are characterized by the distribution of predominantly rocky and coarse built coastal bluffs, and with the same success this procedure can be applied to the coasts of any climate zones of Earth.
In essence, a universal tool is proposed, which, like DSAS, is not limited by the Arctic, and therefore the choice of The Cryosphere as a journal for publication does not seem obvious. Moreover, the results obtained are not interpreted by the authors in any way from the point of view of the peculiarities of the evolution of the Arctic coasts; the role of the geomorphological structure of the coasts, the presence of permafrost and its ice content is not considered in any way, which is the subject of discussion in publications on the landscape dynamics within Earth’s cryosphere. The information given in the Introduction about the dynamics of the Arctic coasts, built by the ice-rich permafrost does not correspond to the characteristics of the study areas. Actually, the manuscript does not contain a detailed description of the study areas, such as the structural features of the coastal cliffs, the onshore and offshore geomorphology, the sediments composition along the coastline, permafrost characteristics and ground ice presence.
The Discussion section discusses mainly technical details, such as classification accuracy and the position of the obtained coastlines from the reference ones. There is no geomorphological interpretation of the results obtained in the manuscript, nor is it in section 3.3 Examples of geomorphological applications. The natural component that makes the Arctic coasts a special, in many ways unique object of study is not highlighted in the article.
Thus, the authors have proposed an interesting approach for studying coastal dynamics with a comprehensive analysis of a time series of satellite imagery, but the manuscript is still just methodological. In light of the above, it seems to me that the proposed manuscript is not entirely suitable for The Cryosphere journal, but is more consistent with the topics of EGU journals focused on geoscientific, geoinformation methods and approach. Therefore, I suggest that authors consider the possibility of redirecting the manuscript to one of the following EGU journals: 1) Geoscientific Instrumentation, Methods and Data Systems (GI) or 2) Geoscientific Model Development (GMD).
kind regards
Citation: https://doi.org/10.5194/egusphere-2023-1399-RC2
Data sets
Arctic shoreline displacement and validation data for two pilot study areas Tua Nylén, Mikel Calle-Navarro, Carlos Gonzales-Inca https://doi.org/10.5281/zenodo.7993787
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